You are a national treasure sir. I have been watching you videos for a couple years now and always learn something new. You present data in such a great manner to teach people.
@@SchrodingersBox o jave a 08 Chevy Express 2500 6.0 L vortec i jave p0171 p0174 p0300... Ive just found that my pvc hose to have a big crack im the hose right where it hooks to tje head just wondering if this cpuld be my problem im a beginner diyer
@@SchrodingersBox yeah Im waiting on part too get here but I unplugged the hose where it plugs in at valve cover and hooked scan tool up reading trims...my long terms and short terms with PCV valve hose off were both at 24% plugged it back on and short term dropped back to where it normally is after a minute.. Just a thought
Matt, I want to sincerely thank you for making this video series! I have a 99 Silverado NBS with the 5.3L. I've been trying to troubleshoot the cause of my P0171/P0174 for 2 months (due to lack of time and money). This series really hit every possibility, in the fastest and cost effective way, and you are a true "troubleshooter"... and that comes from a guy who is a troubleshooter on fighter jets. 2 days after watching the entire series and taking lots of notes (like you said, don't just stop when you find 1 possible issue) my truck was fixed! and I don't have any of the cool toys you do. THANKS BUDDY!!!
I have p0171 on 2011 gmc savana with a 4.3 engine , what’s strange is the fuel trims are about -14 at both banks , I am really puzzled , what’s your input on this, appreciate your lectures
I have quite a few videos on rich fuel trims but you usually want to start with fuel pressure first. Then consider any possible improperly metered induction or extraneous fuel sources entering the combustion.
most common problems with po171 dirty maf, fuel delivey and vacuum leak. freeze data show the problem is only under load that eliminates vacuum leak. the problem only affects 1 bank which eliminates dirty maf and fuel pump. o2 sensor shows rich at wot and switching normal. I would check fuel injectors on bank 1 with a fuel injector pulse tester and check that each injector delivery the same amount. thanks for your videos I learned so much from them.
paul miranda Dead on Paul- your thinking is right on. We will do the balance test for sure. Any other things you can think of that might also explain the results and how we would test them?
I just had had a toyota with both banks STFT at 8 and LTFT at 52 and P0171 & P0174. Turned out to be a piece of fuzz wrapped around the MAF wire. Removed the fuzz and a shot of cleaner and instant fix confirmed on scanner graph. I used all of Schrodingers thought processes to get to the MAF. Thanks Mr Schrodinger. Might I add that AZ free scan wanted the guy to buy a $110 O2 sensor before he brought the car to me.
I was a GM mechanic for 20 years and had a wonderful time, all i did was short blocks and engine rebuilds, I was the only guy on the line who like doing them and i got extremely good at one point, I was young enough to install manual transmissions without the need for a transjack, just pick it up and slip it in. BUT But but....When i had to learn an all cars later, I was spoiled and had no experience, I got over it, but was never as good with any other cars, Nice video.
i just found your channel while trying to fix a 5.7 that hesitates. i like your format (instructor giving quizzes) and you are quite entertaining. keep it up! ever spend some time with performance Audi products? be careful, I used to think American muscle knew no equal. rs7 Performance Premier made me reconsider. being a physician you are able to test drive one without being an imposter/ tire kicker. do so. Those Germans are pretty sneaky a 4 door super car, its almost criminal.
A long, long time ago...you were my most watched channel and probably one of the first I subscribed to. Then for some reason that only UA-cam can explain, you disappeared from sight...and short term memory. Fast forward to current time...VR6 fuel trim issues. Upon doing some research, came across these amazing videos from years back. Still some of the best out there. Just wanted to convey my appreciation for the help. Hope all is well.
I love all of your videos that I've seen, but the graphical representation of the "ricer flyby" made me laugh out loud. Just one more reason I love watching these.
Hi Matt, a fantastic video, I have liked a lot of the questions during the diagnosis, this time you will overcome. Please, I would like to do more videos like this. Thanks Master, thanks for your time and for sharing your knowledge with us. Thanks Matt.
If I suspect a part is the problem I usually check it with a multimeter where applicable and I clean sensors, check vacuum lines etc. Need to watch this one a few times Matt and I am going back over the fuel trim videos too. Great channel.
You're a great instructor. I got the right answer right off the bat! But, I didn't watch your fuel trim videos multiple times. Repetition is good for old dogs.
What i'd do is, disconnect all four of the fuel injectors electric connectors. (He's furious already) use a paper clip to jumper those connectors to send directly through the pcm with no load, find a soft part of that trans am and set it on fire, then buy you something made in Japan, this concludes my diagnostic suggestions. Lol btw thank you Matthew, for a highly entertaining and super informative channel.
Haha my personal car is a mustang with a big ol v8. Actually if you watch a ton of this channel, the above paragraph is like a distillation of his pet peeves, be it a 1.2L racecar running 50lbs of boost, or shorting directly to the ECM.
I like your videos a lot, I learned a lot from you, I feel sorry for those stupid comments from ignorant people, what they don't know is that they waste there own time, thanks Matt.
Man, you had me for a second there! How about I fly you down here and you can do a case study on this one. It has me beat. I just spent 2 hours confirming O2 signal on both banks is getting to the computer- it is, and O2's switch and react correctly with vacuum leak and propane. No vacuum leaks at all- verified with a smoke pro (smoooke Prooo as you'd say lol). Cleaned MAF. Why is this stupid thing showing lean under throttle? Got more videos coming up this weekend if you or your students want to take a stab it.
Schrodingers Box Hi Matt did you consider my thoughts on the air injection pump as a vacuum leak . The smoke test would not have shown a leak there. Although the pump was not active during your testing, would it not be possible for the valve on bank one to leak O2 into the exhaust manifold and cause a false lean condition. Danner would be the guy to know how to verify a bad check valve on bank one or is it even plausible . Is there a spot to smoke the AIP lines and see if it holds pressure ?
Matt, have you checked exhaust back pressure? If you have a dual cat system maybe the one bank that isn't plugged is getting all the fuel and the bank that is plugged is therefore having lower trims. Worth a shot, you've tried everything else that is logical. Keep on doing these videos, their fun.
Rear O2s react identically to environmental variables and aboslutely no drivability problems = no clogged exhaust but good idea for a bank specific idea. This problem is not bank specific I believe, at least as far as a mechanical issue.
Matt. I just wanted to let you know that during the valve adjustment I performed myself on my 2006 Acura TL, I used your method of turning the crankshaft with an over-set torque wrench as a massive ratcheting breaker bar from the land of intelligence. I have multiple misfire codes during WOT. (P0300, P0301, P0302, P0304, recently P0306, all usually pending unless I keep the WOT going despite the flashing CEL.) it appears the misfires begin at 3,000rpm, but below that, there is no misfire count. I recently installed an OE fuel pump module, as while chasing this misfire condition for over a year prior to finding your channel, I had installed a Delphi fuel pump module in February as part of a near weekly parts cannon entry because I found it for cheap and figured the in tank fuel filter neede-… you know already. It turned out to cause a starting condition, P0171, 01714, and driveability issues that were rectified by the genuine fuel pump module, whereas the Delphi pump did not originally fix my misfires. I am now suspicious of my injectors, but this unforgiving, returnless system with integrated pump, filter, and pressure regulator, and no way to test fuel pressure under load to my knowledge due to needing to remove the intake manifold to test fuel pressure at the rail, I’m feeling stumped. I lack scopes.
Ok so what data do you have? If you don’t have fuel trim data, fuel pressure data, timing data, compression data, or spark output data I’m not sure what you are going on that indicates a fuel pump was bad?
@@SchrodingersBox looking at STFTs and LTFTs and their reaction to throttle led me to replace the pump which did resolve the P0171/P0174. the multiple cylinder misfire under load issue had been happening prior and continued after replacing the pump
@@SchrodingersBox LTs were maxed out at 18.8 and short terms varied but always increased and then leveled out when I raised the RPM. car is MAP only. I should have mentioned in my ramblings earlier that I recently did a timing belt kit. car has always sounded like compression is good in “clear flood” scenario (with fuel pump relay removed or Delphi fuel pump after 8 months) as well as numbers have tested in the high 180 range
I don’t see how you conclude a fuel pump from that but whatever the case there unfortunately isn’t any data here to be able to even get a direction. Wish I could help but there’s nothing to be able to even determine a direction with.
So i answered all your questions correctly. Haynes Manual jockeys...? Back in my younger days a friend of mine put petrol in their new diesel car, easy done when you convert to a diesel after many years driving petrol cars. New cars have an Anti-Syphon mechanism down the filler spout so getting out the fuel without taking off the tank was not easy. He paid a garage to have the fuel taken out and a new fuel filter fitted for a rather large cost. A Haynes manual indicated where the fuel tank could be accessed from without removal, this was under the rear seat and could be done without taking out the fuel tank. The large charge from the garage could have been avoided by reading a Haynes manual to locate such a easy simple port hole to remove the tank cap an fuel lines to syphon, clean and do the work yourself. Since this i consider information provided by the Haynes manual very valuable, as for Scotty Kilmer, Y U hating on him? Fuel injection is a wild fairground ride of fuel economy and performance but Carburettors sound and make you feel good. Can you tell, I have a passion for naturally aspirated engines with float bowls...? Nothing beats the sound of a wide open Dellorto/Webber butterfly with trumpets.
your awesome dude. been a mechanic most of my life, you make it fun again. And leave old scotty alone, hes a good informative guy as well. Gene ps my 2001 4.3 jimmys 171 and 174 codes have been driving me nuts. im not a parts changer but i'll figure it out.
Thanks. If you have both the 1 and 4 you want to think of what would affect the air metering for the whole engine. Induction sensors, fuel pressure and leaks between the TB and MAF are all usual suspects
OK, a car running lean on one bank. We can eliminate MAF, MAP, O2B1 because of .1 -- .9 swing, I think that leaves us with bad fuel injector. A power balance test is in order?
I have never heard of an injector power balance test. Interesting. So, maybe a clogged or malfunctioning fuel injector in bank one? I would like to learn more about this possibility. But, let's say that one out of four injectors is malfunctioning. When the injector fuel delivery pulses are increased in all four injectors to compensate I would imagine that would cause a mis-fire in at least one cylinder. Plus, the fuel trim seems to increase more when driving the car at rpms versus revving the car while in neutral. That to me says exhaust manifold leak because of the torque on the outer engine caused by the drive shaft.
Well I failed that test miserably. In my own defense I'm an OBD-I owner and fuel trims are a foreign concept. I laughed my ass off because you did indeed get me and absolutely loved the answers. Brilliant.
Yes obd1 G M has fuel trims. Stft are intergator and ltft are block learn with a scale of 255 being lean 128 being 14.7 to 1 anything under 128 going rich.
I have a special version of Ford EEC-IV installed in a Mazda where Ford unkindly removed the live data port capability. Otherwise I would have the same ECU setup as a Mustang. :(
***** Yes, for the most part, eec V is when they went to 16 pin dlc's. Some earlier t-birds (94-95) and lincolns had 16 pin dlc's, but they were only for ABS and SIR diagnosis. Even though there was a 16 pin dlc, one still had to retrieve info from the eec iv connector under the hood. I rarely use mode 6 except to view evap data. There's good info in mode 6, I just have other ways of seeing what I need to see. Remember, mode 6 is one the federal side of the PCM, not the manufactures side, and theres more data on the manufactures side of the PCM.
Wow great videos!! Im learning soo much, plus learning how to properly read my code reader... still don't know why all of my banks show a 24- 35% positive lean on all my STFT and LTFT.. but ill keep watching to hopefully find out. Lol
This was an AWESOME video, 🙂, i bet 'Scotty' really watches this channel too 🤥!! i always crank up your video's to 1.7 X above the 'normal' speed, as then it sounds like you're kicking ASS !! Thanks for all that you do, and please keep up the great work , Bless 😇
@@SchrodingersBox nah, nothing resembling a 'chipmunk' 🙂, just simply AWESOME, and not for faint hearts, for individuals who aspire to be 'PIONEERS',,,but you lead the pack,,by a mile,, 😎👍,,keep up this top shelf, high octane,turbo charged, multi faceted education 🙂
Thank you so much for all of this. I am getting a lean condition bank 2 CEL after decelerating or coasting. I am getting misfires also mostly on cylinder 8. Its not the maf, map, or 02 sensors. coils wires and sparkplugs are also new.
Another good video you're kind of right about Scotty he's just trying to make a living too and keep the local auto parts stores in business thanks for the education
Using the scan tool I would test the fuel trims and O2 sensors at idle by producing a small vacuum leak in say the brake booster line. Determine if everything (Bank1 and Bank2) responds as expected to a small lean condition. Spray some propane into the small leak and see if everything responds as expected. Basically, go to a known "good" condition and perturb it and see if you get the expected result.
Regarding further testing to diagnose your P0171 issue, First, I would go to Mode $6 data, in Global OBD II, to see if there are any active misfires to identify the offending cylinder(s). If yes, then I would consider an injector balance test (assuming I had access to an fuel pressure gauge and I could activate individual injectors with a bidirectional scan tool (If no bidirectional capability or support, then use a Fuel Injection Pulse Tester (e.g. OTC 3398)). If no misfires, then I would pursue an exhaust leak. To test for exhaust leaks, obviously one would need to smoke test the exhaust with a smoke machine (e.g. Smoke Pro).
Great videos. I'm here a little late for the quiz. First time learning how to troubleshoot with a scanner and came across these vids. Anyways, greetings from Grand Junction CO.
@@SchrodingersBox Wow! Crazy news on TV tonight... Anyways, man I Love the Trans Am. My dream car. I'm facing the fun P0171/P0174. Unfortunately my scanner doesn't have a long enough cable to watch STFT as I spray carb cleaner searching the vacuum leak. Truck is 2003 F150 5.4 2v. I have 28% LTFT on both banks. A smoke test is definitely what needs done at some point. I don't have a smoke machine but plan to try and make a simple one. My guess with my beginners knowledge is that I have a intake manifold leak on both sides. Hoping I'm wrong, because that's a big job for me working under a shade tree lol.
Hi Matt, Great Stuff! Got to keep doing them like this. The Injector Balance sounds logical for Direction to me because I believe you said you have a Schrader Valve handy on the Fuel Rail to hook up a Pressure Gauge. It make for a quick and easy start in your Direction. But it also raises some questions. If one Injector is somewhat restricted and or partially shorted internally, would you not get a hiccup/dry misfire under load? Also if the Injector was restricted, at WOT why is the Bank 1 O2 going fully rich? If you are saying that the Computer is calling for more and more fuel because it is detecting a lean condition under load and that is why the O2 is going rich. At WOT and the engine is inhaling tons and tons of air, would the Computer/Fuel Trims be able to compensate for a partially dry cylinder, enough to send your Bank 1 O2 fully rich? Just a hunch, could there be a small exhaust leak upstream of your Bank 1 O2, or could the bank 1 O2 be a little lazy? Just a hunch, not a guess, so I dodge the punch in the throat.
Billy R Ha no throat punches when your arguments are valid- and they are not only valid but sound. I did not show it but there are no misfires at all even under load (which is when you would expect them and actually surprises me). But regardless you are dead on and the suggestions will be executed in next video.
Injector balAnce test on bank 1..Matt you are natural, great showmanship you should submit some your vids to one of automotive channels get a 30 min segment for engine performance diagnostics..
fivefortyeye540i Thanks 540, and agreed- injector balance test would be the easiest to do given that I have AutoEnginuity and a schrader valve on the rail. We'll see what happens as the channel grows lol but yeah I started to get like that crazy guy on Fast n Loud for a minute there lol
I would do a bank 1 sensor 1 response to a man made lean condition (vacuum leak) and see if there is a lazy O2.Then a injector balance test with fuel pressure gauge connected to the fuel rail. Record rest pressure then energize each injector with a timer and compare the fuel psi drops.
Schrodingers Box so your just a parts changer lucky you don't fix cars for a job this is not how to fix cars by just switching parts and seeing if its fixed I know its the easy way and this is how most people fix cars .but your UA-cam channel was all about the science of how to test and be 100% it was the part before we fit new parts not just switching parts from one side to the next or from one car to the next please lets us all know that I am wrong about this thanks
Check the vacuum lines to the brake booster and PCV. ScannerDanner made a video on a Pontiac that had a brake booster issue causing a vacuum leak which then dumped fuel during load. What are the chances you've crisscrossed vacuum lines during a previous project? It's not a bad fuel pump because the car would be misfiring during heavy acceleration as the injectors dry fire. You would definitely see P030x codes for that one. On my car the PCV is between the MAF and TB so a leak there would cause an issue on both banks (not your issue) however also on my car is an EGR that only receives part of the EGR gas from 1 bank not both. Depends on your car configuration and really helps to know the Trans Am in this case (which I do not). Worth mentioning to your viewers that this kind of thing can be caused by a vacuum leak in the EGR system if that system is only on 1 bank. Since EGR only operates during specific times programmed in the ECU you might see different circumstances where A/F is affected. 18% TPS @ 30 mph (light throttle and cruising speed) seems bang on for an EGR leak if your EGR is only pulling from 1 bank like mine. Since you have one of those snazzy OBD-II thingies you can pull up and compare EGR data against fuel trim. Again depends on the specific vehicle but an answer on par and worthy of the intellect you expect from your subscribers.
EGR has no effect on A/F ratio on a MAF system, and hence would not have any effect on fuel trims. Your vehicle may only get EGR supply from one back, but it distributes it to both banks once the valve opens. I'm not aware of any vehicles the get EGR supply gas from both banks.
gojudude My point was to check for an air leak in the EGR system. I had an EGR pipe rust through that gave me an endless amount of issues and took me years to find because it was a small pin sized rust spot. That would still show up on the MAP in this system. I don't have a MAP only MAF and it will definitely screw with A/F just like any air leak. I didn't quite think that one all the way through for this case. The MAP acting as a backup was a great design decision. Makes me wish my car had that setup.
***** Checking for an air leak on the EGR system is a valid point. However, The MAP in this system (the Trans Am) has no input whatsoever on fuel distribution, it is there only for EGR monitoring. Nothing more, nothing less. As far as your vehicle not having a MAP, then it has an EGR sensor or some sort, like Fords do with their PFE and DPFE. As for your leak on that pinhole, if it was letting outside air enter through the pipe and go into the intake with the EGR gas, it would have to be an exceptionally large leak to effect trims as EGR doesn't work at idle unless it's a throttle by wire vehicle. Other than that, EGR is inert, and doesn't effect trims on a MAF vehicle because the MAF is not, and I repeat, it is not measuring the volume of air, its measuring the mass, or density of the air, and doesn't need correction by the IAT or BARO like a speed density system does.
My best guess is that you may have a loose or leaking exhaust manifold in bank 1. I would take a bottle of propane and introduce propane along the manifold seal while watching the fuel trim for bank 1. Dropping the hammer on rice burners will create a lot of exhaust back pressure. Separately, I enjoyed the quiz format. I had several DTCs Friday including P0153, P0137, P2098, AND P2096. Afterwards I recorded O2 volts, fuel trims, and rpms on Autoenginuity and I have that file. I diagnosed the problem this morning using the recording. It is a parts changer special right up your alley. LOL. Would you like the file for a future video?
Sandbag1300 Sure I'll take the file! private message me and I'll give you an email addy to attach it. Also good point on the exhaust leak- totally valid and I will test accordingly.
Fantastic Matt you make a difficult subject fun. Ok I'm going out on a limb here taking a chance on getting a punch in the throat , but here it goes. Both O2 went rich on a WOT, so fuel delivery is capable of adding fuel. Live scan data showed adding fuel bank one but you say no drivability noticed. I am leaning towards a fuel delivery problem from injectors on bank one. I would do an injector balance test to see if you have an injector not spraying equally.
Steve Rob Thats about 7 votes for balance test (mine included) and indeed it will be done on the follow up video. Your rationale is dead on. No throat punch, but a ticket to the 2% community lol
Hey, Mat. Will you have a low calculated load value if you have a low fuel pressure from a weak fuel pump, bad pump circuit, restricted fuel filter, and so on? I tend to use the calculated load value for MAF testing. Thank you.
No you won’t. That’s the beauty of a technique called “volumetric efficiency calculation”. Low volumetric efficiency will be completely independent of a fuel deficit issue and helps you rule it in or out.
Hey Matt, on a non return fuel system could a clogged injector on bank 1 cause a lean condition on that bank and a rich condition on bank 2, while under load?
Thanks for your feedback man:-) still trying to trouble shoot my 06 chevy 4.8l. With your vid's and replys we have found broken wire on maf sensor, then tested o2 sensors by adding rich and lean conditions to both banks and found bad bank 1 sensor 1 (heat shield fell free and landed on o2 sensor and wore through a wire) still getting p0300 code, to the point it's misfiring so bad it can't get past 60km/h . At idle bank 1 FT's are +10 , bank 2 FT's are 1.3. Add throttle and bank 1 soars to high + and bank 2 drops to high - , it's a van, so not easy to work on, can't find a vacuum leak, so looking towards injector?
it can’t be a vacuum leak with those fuel trims. It does seem fuel related. Might also try swapping the O2 sensors and seeing if problem switches banks. If it does replace the O2’s. If the problem stays same then I would definitely suspect fuel issue. check fuel pressure on the rail at key on, idle, and 2500rpm. Sounds like a good video lol.
Hey Matt, haven't had the chance to do fuel pressure test yet ( don't have proper gauge) got looking at down stream o2's and bank 1 varies 100-600mv and bank 2 800-900+ and both o2 STFT are locked at 99.2% ?
Matt on yesterday's TPS . I would like to say I don't subscribe to the phrase "the only stupid question is the one you don't ask". Unintended consequences during the test showed me there is no conductivity between a TPS and an IAC. While the TPS was disconnected am I correct to assume if you opened the throttle plate the IAC pintle would have closed and stalled the engine for lack of fuel. Also did the TPS have a ground at the sensor to the ECM provided and why did you need another ground ? I pay close attention to your vids because you do and say things to see if we're paying attention , one "C" in vacuum better not put a "E" LOL , so you have two options - 1 - I'm correct and 2 - I'm Nuts . 😜
Steve Rob Steve, based on other comments as well as yours I do need to revisit the cause of the engine speed increase with TPS and it will involve pulling IAC data. My thinking... which I agree may be wrong... is that the IAC is a non factor since presumably you would expect IAC to close if anything with increase in TPS, so I didn't consider it as reason for idle change. I though idle change was due strictly to fuel addition which of course I did not detect with fuel trims because I wanted to make it so ONLY the MAP and MAF could be used to detect the bad TPS signal. Another analysis is in order to answer the question for sure and this is exactly the reason for my idea of "Schrodinger's Mailbox" where I can revisit stuff like this!
ScannerDanner Yes you are correct Paul, and it held steady BUT later on while driving it reverses and the LTFT's will be at zero but when I accelerate the FT's increase easily 10-20 sometimes more. The "vacuum leak" pattern happens only in the first 10 minutes after CL. The "fuel deficit" pattern happens later and stays consistent. But fuel pressure fine, cleaned MAF, no vacuum leaks confirmed by smoke test (which also confirmed no vacuum leaks). Both LTFT's adapt to variables in generic mode but bank 2 absolutely won't budge in enhanced mode at all- seems to draw a substituted value- but from where?
I enjoy the amount of knowledge I obtain from your videos, they've actually helped greatly getting my grandpa's truck running again. Favorite parts thought are you jokes about that Terd with lips scotty kilmore
Doing a injector balance test is defiantly the next test you should do. But I am going to go out on a limb and say that will not be your problem ! I think you are going to find a air leak in exhaust in bank one. And the o2 is working the way it should.
I second this motion. Check the fuel injection system first. However I would take the exhaust leak test further. The car has an AIR system on it. I would check for leaks and check the components of the Air Injection Reaction System around bank one. I am not completely familiar with this system, but after looking at the AC Delco site. I think I see what could go wrong with the system.
What would be interesting is a person with a common problem and the ability to provide graphs as needed to provide you with ongoing requirements as required by yourself and then attempt to diagnose the problem.
Hello, not sure if you’ll respond but I’ve been learning a lot from you lately Thanks to your videos. I am getting bank 1 and 2 lean codes. While driving, my short fuel trims shoot up to 28-32% and go back down after letting off the accelerator. Starting to think I have a bad maf sensor. I’ve cleaned the maf sensor as well.
@@SchrodingersBox on it! Thank you! Do you offer live diagnostic services or have you considered? I would gladly pay to learn more you through video communication. Appreciate the knowledge every time 👍🏼
@@SchrodingersBox hello, checked fuel pressure and replaced the fuel pressure regulator. Fuel trims are close to zero now. Much better. Still getting lean conditions unfortunately. I checked my catalytic converter readings and I am not liking them. Pre cat sensors on both banks are reading normal (fluctuating up and down as they should), but my o2 sensors after the cats are not. Bank 1 o2 sensor 2 is stuck at .500 mv, bank 2 o2 sensor 2 is stuck at .100-.200 mv. Correct me if am wrong but aren’t both o2 sensors after the cats supposed to be at above .600-.700 mv? The weird part is that am not getting Cat deficiency codes. Only lean codes. Also shrt fuel trims keep climbing only when accelerating. They Settle back down to low single digits after decelerating or at idle.
So what kind of glass packs do you have on your Fire Bird. I had a '69 Tornado with duel exhaust and walker continental glass packs that sounded so mellow with that 455 cu. in. high compression engine under the hood. Last year they made that engine in a high compression model. So cool when the smoke would curled around the front fenders. That was a big step up from my Morris Minor.
I don’t use glass packs since I am maximizing performance. I lowered compression to 10.55:1 and put in a procharger supercharger with 9lbs of boost. The exhaust is a SLP Header and Y pipe combo with Borla exhaust. Absolutely zero backpressure even under load. 710 RWP at 5200RPM is the final dyno-tested result.
I am new to this and learning, I would look at testing fuel pressure and see if the pump is not working correctly. If the pump is weak wouldn't that effect all banks and injectors, unless one injector for bank one is clogged. O2 sensor would be what I think the issue is
correct on the fuel pump- it would affect all injectors. however we know the O2 sensor isn’t the issue because of the fuel trim response. it’s definitely not an O2 sensor issue.
No because we see no misfires or injector pulsewidth correction. keep watching to the end of series- it continues on another series. look in description on last video
Hi Matt, I like the game that you proposed, I would review the injectors bank 1, A shorted injector would do the O2 sensor will report lean.When we accelerate the amount of fuel is not sufficient and PCM open more time the injectors, because of this we see increases LTFT at banc 1. I think the problem with this car is a short injector, wiring fault or fault pcm signal to open a injector. Thanks for your class Matt,
What you describe is an open injector. A shorted injector will constantly dump fuel causing an extremely, extremely rich condition. But even so- if there was an open injector- you are right, there would be a lean condition on the bank due to the unburned oxygen HOWEVER the lean condition would be present even at idle AND there would be misfires every cycle and driveability problems. It is definitely not a shorted or open injector (which will be shown on the balance test) but it could definitely be unequal fuel delivery from an injector- i.e. partially clogged. However the fuel trims at WOT argue against that too. But your thinking is very accurate.
I had an issue recently with my 2002 Holden Commodore which runs the 5.7 litre Chevy LS1 engine where I drove it after that it sat outside for a few days & had a hesitation when cold. After I filled it up with fuel the next day the CEL display came on & the fuel trims Maxxed out at 25% on both banks,for whatever reason,my scan tool didn't read a lean fault code. I tested the fuel pressure which was at 47 psi (it should be at about 60 psi) & the fuel pump was noisy. I decided to replace both the fuel pump & regulator for just under $50 AUD (the whole fuel sender costs about $100 AUD on EBay),the regulator is a Buick park avenue one which I bought for $9.99 AUD,the pressure had to be adjusted in a bucket of fuel whilst running the engine,it was set at 61 psi which is the best I could do. The fuel trims today were at 10.94% on both banks @ 100 km/h (60 mph) at cruise speed with an ambient temperature of 23 degrees Celsius & a coolant temperature of 100 degrees Celsius. Fuel trim under load was at about 7 - 8 %. So I'm glad that problem is all sorted out now.
I'm looking at the graph. I truly believe it's the O2 sensor. I clean mine up just a little bit not too long ago. And then on day two it came back up only because I cleaned it, but I didn't use. Gasoline like they say you should use. I use brake cleaner to clean it off. But I will be doing a smoke test real quick. Just curiosity.
Based on your quiz questions, I would select bad O2 sensor, but why wouldn’t fuel injectors be a suspect here? Fuel pump and maf would affect both banks so those are out, but couldn’t fuel injectors also be a possible problem here?
I'm actually very excited to find out the cause because I have similar problem with my Corolla :D. LTFT goes high under load. I have of course looked for simple and unlikely stuff like spark plugs, vacuum leaks and other leaks and did O2 response tests (was switching fine and did respond to lean and rich condition). Then I had my fuel pressure checked which was perfectly within specs. Then I took my injectors out and cleaned them (not much dirt came out) and spray pattern looked fine to me in all of them, so no much effect. I came to conclusion that my MAF was going bad and replaced it (of course I tried to clean it before). And it had a BIG effect on LTFT, dropped from +10 to 4 at idle and from +20 to 12 under load. But the characteristic is still there, so what the heck could still be the problem? Of course there was no way for me to measure fuel volume of injectors so they could still be potentially the issue. I also don't have any drivability issues, just a little higher fuel consumption. And as for this Trans am case, I think the problem is with injector(s), maybe clogged/dirty.
Von Brontos We shall see! If your corolla was a 4-banger then all your diagnoses were valid, but if it was a 6-banger, hopefully now you see that much of the tests could have been ruled out. Cleaning a MAF is a good idea anyway though- I do it every air filter change.
Just curious what you learned on scotty’s channel? I have yet to see one single useful EVIDENCE DRIVEN diagnostic information whatsoever. all I ever seen is parts cannon ridiculousness and “these computer controlled cars are crap- don’t bother with them” kind of stuff like you see in the automotive chat room forums from people clueless on technology and diagnostics. The day I see him do a cam sensor bypass instead of throwing a cam sensor AND a crank sensor at a cam sensor code I think I’ll fall out of my chair.
yeah . i was kidding i find what you offer and how to explain is very useful and is not competitive for you . i have learned so much in this short period . thank you so much for this \ i am not very good in writing English . but i speak well / .
Thank you for your very informative video bro👍👏 I have an Audi A6 2008. Vehicle: Audi A6 C6 4F 2.0L TFSI 2008 (4 cylinders) only one bank. Only P0171 no other codes. System too lean at idle bank1 Freez frame DTC : P0171 Engine load : 20.8 % MAF : Air flow rate. 3 g/s RPM: 742 Fuel rai pressure: 688.92 psi Short term fuel % trim : 3.125 % Long term fuel % trim : 0. % Fuel / Air ratio : 14.63 % No apparent vacuum leaks. Any idea, appreciated. Cheers.
Nothing can be said about this data- there is no curve against load. You can neither suspect nor rule out anything from a freeze frame. All we can tell from this is it can't possibly be a vacuum leak and nothing more.
Hi Bro, could you do examples of testing procedures on ASE A1? I subscribe and I always dig all of your content. If you read this question, please let me know! Thanks again for delivering outstanding content!!!
It does show duty cycle, but we already know the duty cycle would be longer because of the high fuel trim. What are you suggesting I look at with the duty cycle that I'm not thinking of?
It would be interesting to see the duty cycle of each injector or even injector pulse width if your injector balance test shows a low flowing injector. Would the duty cycle or pulse width be higher than the other normally functioning injectors? It would be nice to see that type of evidence also.
Ah agreed. I need to check if I can get that. I may be wrong, but I belive that pulsewidth is set for all injectors on the same bank equally- i.e. there is not individual pulsewidth per cylinder- I don't know how the PCM could possibly know which cylinder to adjust pulsewidth for, especially considering no misfires which would be the only cylinder specific indicator I can think of. Makes sense, no?
I Enjoyed your video. I am trying to research the chemistry and mathematics of oxygen sensors so I can have a better understanding of sensor failure modes and how other problems will affect the sensor. There is a huge amount of misinformation out there . I having differculty working out what statements are correct and what is wrong. Would you consider doing a high level video on the reaction and how it relates to the platinum catylist and the electrolyte in the sensor.
I am considering it however there is, as you said, a lot of misinformation out there. My current understanding (ha! "Current", get it?) is that the O2 sensor measures the difference in O2 as compared to outside conditions- i.e. it ONLY measures oxygen. However other information some people are sending me (and it's from reliable sources) indicates that hydrocarbons themselves are measured by an O2 sensor. In other words, I would say a rich condition is measured by the absence of oxygen, or in case of too much fuel "the fuel displaces the oxygen lowering the oxygen concentration" if you follow. But, what others are saying is that I am wrong about that and the O2 sensor is indeed measuring the additional hydrocarbons directly. I need to do more research to find out which is accurate and of course come up with an experiment to prove it.
From the info I found the electrolyte moves spare O- that comes from a reaction of O2 with H2 (assumed to be unburnt fuel) and CO . Thus the O- creates a -ve charge on the exhaust side and a positive charge on the reference side. Therefore it is actually a "can further combustion take place" sensor. I will post a link to a paper on it.
My first guess would be an exhaust leak causing the long term fuel trim to go lean overtime. I think this because you're not having any driveability problems. Briefly clog the exhaust while checking for leaks. Is the 02 sensor bias rich a bit on that bank? My second guess would be partially clogged injector causing a lean condition I just think you would notice it somewhat under load. Doing the injector balance test would be good to eliminate this.
We are in total agreement James- thanks for the comment, I believe this is your first on the channel. In dact, I was going to put my money on an exhaust leak until the video i just released today.
At his point I would rule out a vacuum leak because during a load the largest amount of air is metered air and a vacuum leak would be a minor contributor to the problem. I would listen to the injectors for inconsistent sounds comming from one, perhaps with a screw driver used to convey the sound. I would check the voltage on each pin of the injectors relative to computer ground for consistent voltage difference between pins of each injector by back probing the electrical connector. checking for less current draw inside the injector due to high resistance electrical connections or internal failure. These I would test in an effort to discover which injector might be delivering deficient fuel quantity.
Hey @Schrodingers Box I have a terrible experience. I drive 07 Honda CRV 2.0l (Stick/Manual) than lacks power. When I floor it on the road, the car doesn't react to it. But when you pull your leg off the pedal, just before your leg is off the pedal power kicks in. So by deduction, when you lightly touch the pedal, power response. I took the car to a dealer for scanning, first I got a code that AF sensor failure, changed that. They later suspected PCV Valve that was ok. No more codes. Injectors work fine. Fuel pressure ok. Where can I go to look next?
hello Matt. if a car has high STFTs and maxed LTFTs that stay the same with throttle, is it correct that there is not a vacuum leak or a fuel delivery issue? perhaps upstream O2 sensor
@@SchrodingersBox thank you matt. i had a lean code that got worse with throttle that ended up being my fuel pump, but it didn’t fully fix the lean condition. going to attempt to diagnose the wideband AFR sensors since theres 2 and one bank is showing ever so slightly leaner
Good video. I have a p0171 code on my nissan. At idle 800rpm, Short FT -20% and Long FT 13.3%. When at 3000rpm, Short FT fluctuates 0-3.1% and Long FT 3.1%. What could be the possible reason for this?
Dear Sir,I have a BMW E46 316ci .The fuel pressure was damaged ,so low fuel pressure ,so high LTFT (+20,3).After replacement the LTFT is remaining +20,3 but the STFT is -20,3.My question is how long it takes the LTFT to become close to zero in order to drive STFT close to zero? Thanks in advance.
Good video. I'm thinking fuel delivery problem(fuel injector/s) on bank 1. Since LTFT is a learned value you will not see the O2 drop lean. The O2 seems to react pretty normal at idle so I dont see a problem there.. A injector leak down/flow test or swap injectors, depending on whats easiest.
Schrodingers Box I have another suggestion, It would be interesting to watch Mode 6 data. I don't know if Pontiac have misfire data but I say its worth a look. So what I'm going for is to see if the computer can detect any misfire and which cylinder/s. You may have to clear the FT memory to have best chance of see anything.
if your there i have good question i think. Have you ever taken an exhaust off to do a transmission perhaps. And when you were all done you had a system too lean. fuel trim suggest its a vacuum leak. how would i eliminate an exhaust leak?
Can’t think of a time i didn’t have to remove an exhaust to do a transmission. a standard part of the R&R. Usually i just soap water test for exhaust leaks.
One question hitting all the time on my mind is that if a code is lean mixture why fuel trims are positive? Because positive fuel trims means ECM is adding fuel. And negative fuel trims means ECM subtracting fuel trim. Am I right?
if the 02 sensors are reading rich which means theres too much fuel it excludes bad fuel pump/low fuel pressure. but if the maf sensor is bad it can trick the fuel system into thinking theres too much air which will cause a rich mixture and both o2 sensors stuck on a rich condition. does that sound correct?
Haroon Ali It is indeed correct except that we can rule out MAF in this case because the car is only lean on one bank and the MAF would equally affect both banks.
Yes I did but we are looking at a lean condition on one bank under load as our problem. Rich on both banks at WOT is normal if anything that confirms 100% it cannot be a dirty MAF. For the reasons you mentioned- if there was a MAF problem where more air was coming in than being measured, we would see lean on both banks at WOT. I recommend watching my fuel trims video Haroon as it also explains MAF sensor as well as fuel trim.
2007 GMC Yukon 5.3L Engine: I get a P0171 code when running the engine with the AC on for about 20-30 minutes. Vehicle begins to jerk and shake on idle. After the vehicle cools of or I turn off the AC, it eventually returns to normal function. Any ideas?
I'm having issues with an 08 C6 LS7 swapped in a first gen. Lean condition on bank 1. 24 to 25% fuel positive trims at idle up to 1200 rpm goes away at 1300+. Watched all your fuel tr videos and co vince'se it was an intake or vacuum leak. However using carb clean or water sprayed on intake and injector pockets I get no increase in throttle or sound . Where next
So are you staying a vacuum leak in the actual valley cover? I did replace the intake gasket after the spray carb choke cleaner around the top side of intake and all injectors produced nothing. I'll look into smoke test
Hi Matt, I see the video again and I have a new theory, It's possible the car has an injector dirty?, We have a problem with the fuel pressure in bank 1, the fuel pump and regulator fuel are common to both bank, but the injectors are individual for each bank. I think an injector is dirty in bank 1 or the injector has a voltage drop by a bad connection and not open enough. When accelerate there is not enough fuel for a stoichiometric mixture and PCM prolongs the opening of the injector. Thanks for this exercise Master.
Nice video, thanks! In my car I don't see any error codes yet but the following tests always failing MID:$70 TID:$01 Rich to Lean sensor threshold voltage(constant) - Max: 450.63% Min: 61.78% Test result value: 655.20001% FAIL ---- MID:$81 TID:$19 - Fuel System Monitor Bank 1 Max: 4 Min: 24,657 Test result value: 6,528 FAIL ---- Where do you think I should start ?
I have a very odd issue with my 05 Nissan Pathfinder SE off road v6 4L. I had the p0171 code, but for some reason, it only trips at load after warm up. Something seems to click on, and I can watch the live data just start running up to 25% and staying there until it cools down and is restarted hours later, when it goes back to correcting the fuel trims. Also, the bank 2 sensor 1 goes up to .9v and stays there rich on bank two, so I'm not sure why this happens in conjunction with a lean bank one unless there is a manifold leak on the bank 1 side and all that extra fuel is still registered on the bank two (I swapped out this a/f sensor and captured the same exact readings for both sensors, which also means the old factory one I put back in it is probably still good). I've been putting off ripping into the exhaust manifold in fear of stripping something out without having the proper tap and dies to bail me out. I might lube it up and gradually give it a go and at least see if I can find any leaks hooking up my vacume to the tail pipe. Lol jk vacuum. Sorry, I couldn't resist 😹. I just don't understand why it only occurs under load. Could I collapse a hose or something, or when the fan kicks on or some switch activates it disrupts the O2 sensor signal somehow tricking the computer. Idk. Is there a load switch or something that would just all of a sudden cause the one side of the engine to go lean and the other side to be normal.
This is a pretty tough one! Of course, being the cheapskate that I am, if the there is no drive-ability problem, (which you have ascertained that you don't have,) I will be shopping for black electrical tape over the check engine light:-) Given the O2 traces at WOT, it is obvious that both banks are being controlled properly by ECM. I would be interested to see how the LTFT is trending towards the high value e.g. reset and watch. Is it drifting towards the higher value or reaching it pretty quickly? If the ECM had capability of being able to control the fuel trims up to 50%, would this be even an issue? LTFT is there to account for general wear and tear. Of course, we want to know what would cause one bank to need that extra positive LTFT? I can understand one clogged injector but the car is behaving as if one bank is needing consistently more fuel than the other. How is the EGR plumbing on this vehicle? Is it possible that problems in the EGR flow would affect one cylinder lot more than the other? I do remember this engine having some bizarre issue which turned out to be clutch switch or something like that from your early video. I got hooked on to your channel from that video. I have not gone back to see if the previous problem was similar or not.
I like the idea of EGR plumbing but it feeds to the intake right behind MAF so it would necessarily affect both banks... though, come to think about it, the EGR is sourced from each exhaust manifold so there is potential for a leak on one manifold connection. Hmmmmmm. CPS can be ruled out because it would affect both banks since it causes anticipated fuel adjustment.
I have a lean code I’ve been trying to diagnose for a while now. Your videos have been very helpful but I still can’t pinpoint the problem. My fuel trims are fine at idle but but my LTFT jump up to 40% under load. My freeze frame shows usually at 2k rpm. Cleaned my MAF, inspected and changed my fuel filter, cleaned my injectors code still was there. Checked for Vac leaks for the hell of it and nothing. Inspected my TPS and noticed it was out of range so I recalibrated it. Changed the cats because they were 15 years old and the O2 sensors. Changed my injectors along with fuel pressure damper, and my fuel pressure regulator along with my fuel pump because I have a spare. I want to test my throttle body motor and APP sensor because I know they all feed into my fuel trims. Is that a good next step? Any information on how to test these? Any help would be appreciated.
i will go after injector balance test and check the o2 sensor not mass air flow sensor or vacuum leak for the reason of this last two will affect both bank at same time with same readings on fuel trims
![Short Term and Long Term Fuel Trims Explained [Easily]](http://i.ytimg.com/vi/IuM53mlOgHs/mqdefault.jpg)
You are a national treasure sir. I have been watching you videos for a couple years now and always learn something new. You present data in such a great manner to teach people.
Wow, thanks!! much appreciated!!
@@SchrodingersBox o jave a 08 Chevy Express 2500 6.0 L vortec i jave p0171 p0174 p0300... Ive just found that my pvc hose to have a big crack im the hose right where it hooks to tje head just wondering if this cpuld be my problem im a beginner diyer
It’s possible but not very likely. pCV usually doesn’t draw enough vacuum to cause that but fix it and see!
@@SchrodingersBox okay thanks for replying
@@SchrodingersBox yeah Im waiting on part too get here but I unplugged the hose where it plugs in at valve cover and hooked scan tool up reading trims...my long terms and short terms with PCV valve hose off were both at 24% plugged it back on and short term dropped back to where it normally is after a minute..
Just a thought
Matt, I want to sincerely thank you for making this video series! I have a 99 Silverado NBS with the 5.3L. I've been trying to troubleshoot the cause of my P0171/P0174 for 2 months (due to lack of time and money). This series really hit every possibility, in the fastest and cost effective way, and you are a true "troubleshooter"... and that comes from a guy who is a troubleshooter on fighter jets. 2 days after watching the entire series and taking lots of notes (like you said, don't just stop when you find 1 possible issue) my truck was fixed! and I don't have any of the cool toys you do.
THANKS BUDDY!!!
My pleasure, glad you "get it". Thinking types will enjoy this series very much.
I have p0171 on 2011 gmc savana with a 4.3 engine , what’s strange is the fuel trims are about -14 at both banks , I am really puzzled , what’s your input on this, appreciate your lectures
I have quite a few videos on rich fuel trims but you usually want to start with fuel pressure first. Then consider any possible improperly metered induction or extraneous fuel sources entering the combustion.
most common problems with po171 dirty maf, fuel delivey and vacuum leak. freeze data show the problem is only under load that eliminates vacuum leak. the problem only affects 1 bank which eliminates dirty maf and fuel pump. o2 sensor shows rich at wot and switching normal. I would check fuel injectors on bank 1 with a fuel injector pulse tester and check that each injector delivery the same amount. thanks for your videos I learned so much from them.
paul miranda Dead on Paul- your thinking is right on. We will do the balance test for sure. Any other things you can think of that might also explain the results and how we would test them?
I just had had a toyota with both banks STFT at 8 and LTFT at 52 and P0171 & P0174. Turned out to be a piece of fuzz wrapped around the MAF wire. Removed the fuzz and a shot of cleaner and instant fix confirmed on scanner graph. I used all of Schrodingers thought processes to get to the MAF. Thanks Mr Schrodinger.
Might I add that AZ free scan wanted the guy to buy a $110 O2 sensor before he brought the car to me.
Trust me. This is not wasting my time. Your videos are golden.
I was a GM mechanic for 20 years and had a wonderful time, all i did was short blocks and engine rebuilds, I was the only guy on the line who like doing them and i got extremely good at one point, I was young enough to install manual transmissions without the need for a transjack, just pick it up and slip it in.
BUT But but....When i had to learn an all cars later, I was spoiled and had no experience, I got over it, but was never as good with any other cars, Nice video.
Matt. Your a great tech. I enjoy watching you troubleshooting. All your videos are awesome. Don't be a parts changer.
I appreciate that! Hahaha don’t be a parts changer is a great code to live by.
i just found your channel while trying to fix a 5.7 that hesitates. i like your format (instructor giving quizzes) and you are quite entertaining. keep it up! ever spend some time with performance Audi products? be careful, I used to think American muscle knew no equal. rs7 Performance Premier made me reconsider. being a physician you are able to test drive one without being an imposter/ tire kicker. do so. Those Germans are pretty sneaky a 4 door super car, its almost criminal.
A long, long time ago...you were my most watched channel and probably one of the first I subscribed to. Then for some reason that only UA-cam can explain, you disappeared from sight...and short term memory. Fast forward to current time...VR6 fuel trim issues. Upon doing some research, came across these amazing videos from years back. Still some of the best out there. Just wanted to convey my appreciation for the help. Hope all is well.
Wellcome back... Wondering if you happen to be "BchrisL" by chance? You sound like him.
Schrodingers Box
No, have never used that handle / alias.
it's 2 am and i can't stop watching this channel, damn you mat, greetings from argentina
I love all of your videos that I've seen, but the graphical representation of the "ricer flyby" made me laugh out loud. Just one more reason I love watching these.
Hi Matt, a fantastic video, I have liked a lot of the questions during the diagnosis, this time you will overcome. Please, I would like to do more videos like this. Thanks Master, thanks for your time and for sharing your knowledge with us. Thanks Matt.
If I suspect a part is the problem I usually check it with a multimeter where applicable and I clean sensors, check vacuum lines etc. Need to watch this one a few times Matt and I am going back over the fuel trim videos too. Great channel.
You're a great instructor. I got the right answer right off the bat! But, I didn't watch your fuel trim videos multiple times. Repetition is good for old dogs.
What i'd do is, disconnect all four of the fuel injectors electric connectors. (He's furious already) use a paper clip to jumper those connectors to send directly through the pcm with no load, find a soft part of that trans am and set it on fire, then buy you something made in Japan, this concludes my diagnostic suggestions. Lol btw thank you Matthew, for a highly entertaining and super informative channel.
Had me worried for a second there!!!!
Haha my personal car is a mustang with a big ol v8. Actually if you watch a ton of this channel, the above paragraph is like a distillation of his pet peeves, be it a 1.2L racecar running 50lbs of boost, or shorting directly to the ECM.
I like your videos a lot, I learned a lot from you, I feel sorry for those stupid comments from ignorant people, what they don't know is that they waste there own time, thanks Matt.
Thanks man!!
First person to explain it where i actually understood. Thanks
I watched parts of this video an all of part 5. I know exactly what your problem is! There is a lose nut behind the wheel :)
Man, you had me for a second there! How about I fly you down here and you can do a case study on this one. It has me beat. I just spent 2 hours confirming O2 signal on both banks is getting to the computer- it is, and O2's switch and react correctly with vacuum leak and propane. No vacuum leaks at all- verified with a smoke pro (smoooke Prooo as you'd say lol). Cleaned MAF. Why is this stupid thing showing lean under throttle? Got more videos coming up this weekend if you or your students want to take a stab it.
Schrodingers Box Hi Matt did you consider my thoughts on the air injection pump as a vacuum leak . The smoke test would not have shown a leak there. Although the pump was not active during your testing, would it not be possible for the valve on bank one to leak O2 into the exhaust manifold and cause a false lean condition. Danner would be the guy to know how to verify a bad check valve on bank one or is it even plausible . Is there a spot to smoke the AIP lines and see if it holds pressure ?
Matt, have you checked exhaust back pressure? If you have a dual cat system maybe the one bank that isn't plugged is getting all the fuel and the bank that is plugged is therefore having lower trims. Worth a shot, you've tried everything else that is logical. Keep on doing these videos, their fun.
Did AIR test- negative. will be editing new video wth a lot more diagnostics, AIR is incouded in this
Rear O2s react identically to environmental variables and aboslutely no drivability problems = no clogged exhaust but good idea for a bank specific idea. This problem is not bank specific I believe, at least as far as a mechanical issue.
That scotty kilmer choice though....... 😂😅😂😅😂
Matt. I just wanted to let you know that during the valve adjustment I performed myself on my 2006 Acura TL, I used your method of turning the crankshaft with an over-set torque wrench as a massive ratcheting breaker bar from the land of intelligence. I have multiple misfire codes during WOT. (P0300, P0301, P0302, P0304, recently P0306, all usually pending unless I keep the WOT going despite the flashing CEL.) it appears the misfires begin at 3,000rpm, but below that, there is no misfire count. I recently installed an OE fuel pump module, as while chasing this misfire condition for over a year prior to finding your channel, I had installed a Delphi fuel pump module in February as part of a near weekly parts cannon entry because I found it for cheap and figured the in tank fuel filter neede-… you know already. It turned out to cause a starting condition, P0171, 01714, and driveability issues that were rectified by the genuine fuel pump module, whereas the Delphi pump did not originally fix my misfires. I am now suspicious of my injectors, but this unforgiving, returnless system with integrated pump, filter, and pressure regulator, and no way to test fuel pressure under load to my knowledge due to needing to remove the intake manifold to test fuel pressure at the rail, I’m feeling stumped. I lack scopes.
Ok so what data do you have? If you don’t have fuel trim data, fuel pressure data, timing data, compression data, or spark output data I’m not sure what you are going on that indicates a fuel pump was bad?
@@SchrodingersBox looking at STFTs and LTFTs and their reaction to throttle led me to replace the pump which did resolve the P0171/P0174. the multiple cylinder misfire under load issue had been happening prior and continued after replacing the pump
what was the LTFt and STFT reaction to throttle?
@@SchrodingersBox LTs were maxed out at 18.8 and short terms varied but always increased and then leveled out when I raised the RPM. car is MAP only. I should have mentioned in my ramblings earlier that I recently did a timing belt kit. car has always sounded like compression is good in “clear flood” scenario (with fuel pump relay removed or Delphi fuel pump after 8 months) as well as numbers have tested in the high 180 range
I don’t see how you conclude a fuel pump from that but whatever the case there unfortunately isn’t any data here to be able to even get a direction. Wish I could help but there’s nothing to be able to even determine a direction with.
So i answered all your questions correctly. Haynes Manual jockeys...?
Back in my younger days a friend of mine put petrol in their new diesel car, easy done when you convert to a diesel after many years driving petrol cars. New cars have an Anti-Syphon mechanism down the filler spout so getting out the fuel without taking off the tank was not easy.
He paid a garage to have the fuel taken out and a new fuel filter fitted for a rather large cost. A Haynes manual indicated where the fuel tank could be accessed from without removal, this was under the rear seat and could be done without taking out the fuel tank.
The large charge from the garage could have been avoided by reading a Haynes manual to locate such a easy simple port hole to remove the tank cap an fuel lines to syphon, clean and do the work yourself.
Since this i consider information provided by the Haynes manual very valuable, as for Scotty Kilmer, Y U hating on him?
Fuel injection is a wild fairground ride of fuel economy and performance but Carburettors sound and make you feel good. Can you tell, I have a passion for naturally aspirated engines with float bowls...?
Nothing beats the sound of a wide open Dellorto/Webber butterfly with trumpets.
your awesome dude. been a mechanic most of my life, you make it fun again. And leave old scotty alone, hes a good informative guy as well.
Gene
ps
my 2001 4.3 jimmys 171 and 174 codes have been driving me nuts. im not a parts changer but i'll figure it out.
Thanks. If you have both the 1 and 4 you want to think of what would affect the air metering for the whole engine. Induction sensors, fuel pressure and leaks between the TB and MAF are all usual suspects
The best educational youtube channel I have found on diagnosis cars! Great channel wowwowowow thankss
OK, a car running lean on one bank. We can eliminate MAF, MAP, O2B1 because of .1 -- .9 swing, I think that leaves us with bad fuel injector. A power balance test is in order?
Indeed!
I have never heard of an injector power balance test. Interesting. So, maybe a clogged or malfunctioning fuel injector in bank one? I would like to learn more about this possibility.
But, let's say that one out of four injectors is malfunctioning. When the injector fuel delivery pulses are increased in all four injectors to compensate I would imagine that would cause a mis-fire in at least one cylinder. Plus, the fuel trim seems to increase more when driving the car at rpms versus revving the car while in neutral. That to me says exhaust manifold leak because of the torque on the outer engine caused by the drive shaft.
I'm Hooked! 20 year mechanic here and your great!
Well I failed that test miserably. In my own defense I'm an OBD-I owner and fuel trims are a foreign concept. I laughed my ass off because you did indeed get me and absolutely loved the answers. Brilliant.
OBD1 had fuel trims also, they were called integrator and block learn.
Yes obd1 G M has fuel trims. Stft are intergator and ltft are block learn with a scale of 255 being lean 128 being 14.7 to 1 anything under 128 going rich.
I have a special version of Ford EEC-IV installed in a Mazda where Ford unkindly removed the live data port capability. Otherwise I would have the same ECU setup as a Mustang. :(
I think EEC-V is when ford went to a 16 pin ALDL. Mode 6 will have valuable information for you.
*****
Yes, for the most part, eec V is when they went to 16 pin dlc's. Some earlier t-birds (94-95) and lincolns had 16 pin dlc's, but they were only for ABS and SIR diagnosis. Even though there was a 16 pin dlc, one still had to retrieve info from the eec iv connector under the hood. I rarely use mode 6 except to view evap data. There's good info in mode 6, I just have other ways of seeing what I need to see. Remember, mode 6 is one the federal side of the PCM, not the manufactures side, and theres more data on the manufactures side of the PCM.
Great
job explaining fuel trim and problems. Thanks!
Man don't change a thing. Enjoying the channel! I like the to the point teachings and do crack-up often on your sarcasm. (side jokes)
Matt Veillon Don't worry- nothing will change. This style has worked for me very well both inside and outside of UA-cam.
Wow great videos!! Im learning soo much, plus learning how to properly read my code reader... still don't know why all of my banks show a 24- 35% positive lean on all my STFT and LTFT.. but ill keep watching to hopefully find out. Lol
To find out I suggest watching my video “secret of engine problem diagnose - fuel trims”. it explains everything.
This was an AWESOME video, 🙂, i bet 'Scotty' really watches this channel too 🤥!! i always crank up your video's to 1.7 X above the 'normal' speed, as then it sounds like you're kicking ASS !! Thanks for all that you do, and please keep up the great work , Bless 😇
thanks and good tip on the speed but I hope I don’t sound like a chipmunk at 1.7X lol. well then again- maybe that would be even better.
@@SchrodingersBox nah, nothing resembling a 'chipmunk' 🙂, just simply AWESOME, and not for faint hearts, for individuals who aspire to be 'PIONEERS',,,but you lead the pack,,by a mile,, 😎👍,,keep up this top shelf, high octane,turbo charged, multi faceted education 🙂
Roger that!!!
@@SchrodingersBox Be blessed, 😇
Thank you so much for all of this. I am getting a lean condition bank 2 CEL after decelerating or coasting. I am getting misfires also mostly on cylinder 8. Its not the maf, map, or 02 sensors. coils wires and sparkplugs are also new.
Now you can easily diagnose it!
Hahaha.. this my 1st PID to look at.. thanks sir..I have learned a lot from you and all of this make sense now... thanks again
Great to hear from you again!!
Good refresher, thanks Bernie. 🙂
Another good video you're kind of right about Scotty he's just trying to make a living too and keep the local auto parts stores in business thanks for the education
Using the scan tool I would test the fuel trims and O2 sensors at idle by producing a small vacuum leak in say the brake booster line. Determine if everything (Bank1 and Bank2) responds as expected to a small lean condition. Spray some propane into the small leak and see if everything responds as expected. Basically, go to a known "good" condition and perturb it and see if you get the expected result.
Agreed- validation the O2 is reporting accurately is a valid step. I had a different idea on how to do that but will integrate yours as well.
Regarding further testing to diagnose your P0171 issue, First, I would go to Mode $6 data, in Global OBD II, to see if there are any active misfires to identify the offending cylinder(s). If yes, then I would consider an injector balance test (assuming I had access to an fuel pressure gauge and I could activate individual injectors with a bidirectional scan tool (If no bidirectional capability or support, then use a Fuel Injection Pulse Tester (e.g. OTC 3398)). If no misfires, then I would pursue an exhaust leak. To test for exhaust leaks, obviously one would need to smoke test the exhaust with a smoke machine (e.g. Smoke Pro).
johnwrench4speed Dead on as always John. I will actually be doing the balance test using my AUto Enginuity.
Great videos. I'm here a little late for the quiz. First time learning how to troubleshoot with a scanner and came across these vids. Anyways, greetings from Grand Junction CO.
Oh wow man I love grand junction!!! I’m there for work a lot. Thanks for watching!!
@@SchrodingersBox Wow! Crazy news on TV tonight... Anyways, man I Love the Trans Am. My dream car. I'm facing the fun P0171/P0174. Unfortunately my scanner doesn't have a long enough cable to watch STFT as I spray carb cleaner searching the vacuum leak. Truck is 2003 F150 5.4 2v. I have 28% LTFT on both banks. A smoke test is definitely what needs done at some point. I don't have a smoke machine but plan to try and make a simple one. My guess with my beginners knowledge is that I have a intake manifold leak on both sides. Hoping I'm wrong, because that's a big job for me working under a shade tree lol.
Hi Matt, Great Stuff! Got to keep doing them like this. The Injector Balance sounds logical for Direction to me because I believe you said you have a Schrader Valve handy on the Fuel Rail to hook up a Pressure Gauge. It make for a quick and easy start in your Direction. But it also raises some questions. If one Injector is somewhat restricted and or partially shorted internally, would you not get a hiccup/dry misfire under load? Also if the Injector was restricted, at WOT why is the Bank 1 O2 going fully rich? If you are saying that the Computer is calling for more and more fuel because it is detecting a lean condition under load and that is why the O2 is going rich. At WOT and the engine is inhaling tons and tons of air, would the Computer/Fuel Trims be able to compensate for a partially dry cylinder, enough to send your Bank 1 O2 fully rich?
Just a hunch, could there be a small exhaust leak upstream of your Bank 1 O2, or could the bank 1 O2 be a little lazy? Just a hunch, not a guess, so I dodge the punch in the throat.
Billy R Ha no throat punches when your arguments are valid- and they are not only valid but sound. I did not show it but there are no misfires at all even under load (which is when you would expect them and actually surprises me). But regardless you are dead on and the suggestions will be executed in next video.
Injector balAnce test on bank 1..Matt you are natural, great showmanship you should submit some your vids to one of automotive channels get a 30 min segment for engine performance diagnostics..
fivefortyeye540i Thanks 540, and agreed- injector balance test would be the easiest to do given that I have AutoEnginuity and a schrader valve on the rail.
We'll see what happens as the channel grows lol but yeah I started to get like that crazy guy on Fast n Loud for a minute there lol
Excellent diagnostic information.glad i found your channel.
Welcome aboard!
Awesome video, always learning something new from you. 👍🏼
Glad to help!
I would do a bank 1 sensor 1 response to a man made lean condition (vacuum leak) and see if there is a lazy O2.Then a injector balance test with fuel pressure gauge connected to the fuel rail. Record rest pressure then energize each injector with a timer and compare the fuel psi drops.
My thoughts exactly! Though i will test for lazy sensor a different way.
Just a thought. How are you going to Test the the O2 response?
Switch the O2 sensors on each bank. If the problem moves to the other bank then mystery solved, it was a bod O2 sensor 100%
Schrodingers Box so your just a parts changer lucky you don't fix cars for a job this is not how to fix cars by just switching parts and seeing if its fixed I know its the easy way and this is how most people fix cars .but your UA-cam channel was all about the science of how to test and be 100% it was the part before we fit new parts not just switching parts from one side to the next or from one car to the next please lets us all know that I am wrong about this thanks
Schrodingers Box your being a parts changer.
Check the vacuum lines to the brake booster and PCV. ScannerDanner made a video on a Pontiac that had a brake booster issue causing a vacuum leak which then dumped fuel during load. What are the chances you've crisscrossed vacuum lines during a previous project? It's not a bad fuel pump because the car would be misfiring during heavy acceleration as the injectors dry fire. You would definitely see P030x codes for that one. On my car the PCV is between the MAF and TB so a leak there would cause an issue on both banks (not your issue) however also on my car is an EGR that only receives part of the EGR gas from 1 bank not both. Depends on your car configuration and really helps to know the Trans Am in this case (which I do not). Worth mentioning to your viewers that this kind of thing can be caused by a vacuum leak in the EGR system if that system is only on 1 bank. Since EGR only operates during specific times programmed in the ECU you might see different circumstances where A/F is affected. 18% TPS @ 30 mph (light throttle and cruising speed) seems bang on for an EGR leak if your EGR is only pulling from 1 bank like mine. Since you have one of those snazzy OBD-II thingies you can pull up and compare EGR data against fuel trim. Again depends on the specific vehicle but an answer on par and worthy of the intellect you expect from your subscribers.
EGR has no effect on A/F ratio on a MAF system, and hence would not have any effect on fuel trims. Your vehicle may only get EGR supply from one back, but it distributes it to both banks once the valve opens. I'm not aware of any vehicles the get EGR supply gas from both banks.
gojudude My point was to check for an air leak in the EGR system. I had an EGR pipe rust through that gave me an endless amount of issues and took me years to find because it was a small pin sized rust spot. That would still show up on the MAP in this system. I don't have a MAP only MAF and it will definitely screw with A/F just like any air leak. I didn't quite think that one all the way through for this case. The MAP acting as a backup was a great design decision. Makes me wish my car had that setup.
*****
Checking for an air leak on the EGR system is a valid point. However, The MAP in this system (the Trans Am) has no input whatsoever on fuel distribution, it is there only for EGR monitoring. Nothing more, nothing less. As far as your vehicle not having a MAP, then it has an EGR sensor or some sort, like Fords do with their PFE and DPFE. As for your leak on that pinhole, if it was letting outside air enter through the pipe and go into the intake with the EGR gas, it would have to be an exceptionally large leak to effect trims as EGR doesn't work at idle unless it's a throttle by wire vehicle. Other than that, EGR is inert, and doesn't effect trims on a MAF vehicle because the MAF is not, and I repeat, it is not measuring the volume of air, its measuring the mass, or density of the air, and doesn't need correction by the IAT or BARO like a speed density system does.
My best guess is that you may have a loose or leaking exhaust manifold in bank 1. I would take a bottle of propane and introduce propane along the manifold seal while watching the fuel trim for bank 1. Dropping the hammer on rice burners will create a lot of exhaust back pressure.
Separately, I enjoyed the quiz format. I had several DTCs Friday including P0153, P0137, P2098, AND P2096. Afterwards I recorded O2 volts, fuel trims, and rpms on Autoenginuity and I have that file. I diagnosed the problem this morning using the recording. It is a parts changer special right up your alley. LOL. Would you like the file for a future video?
Sandbag1300 Sure I'll take the file! private message me and I'll give you an email addy to attach it.
Also good point on the exhaust leak- totally valid and I will test accordingly.
Fantastic Matt you make a difficult subject fun. Ok I'm going out on a limb here taking a chance on getting a punch in the throat , but here it goes. Both O2 went rich on a WOT, so fuel delivery is capable of adding fuel. Live scan data showed adding fuel bank one but you say no drivability noticed. I am leaning towards a fuel delivery problem from injectors on bank one. I would do an injector balance test to see if you have an injector not spraying equally.
Steve Rob Thats about 7 votes for balance test (mine included) and indeed it will be done on the follow up video. Your rationale is dead on. No throat punch, but a ticket to the 2% community lol
Hey, Mat. Will you have a low calculated load value if you have a low fuel pressure from a weak fuel pump, bad pump circuit, restricted fuel filter, and so on? I tend to use the calculated load value for MAF testing. Thank you.
No you won’t. That’s the beauty of a technique called “volumetric efficiency calculation”. Low volumetric efficiency will be completely independent of a fuel deficit issue and helps you rule it in or out.
Hey Matt, on a non return fuel system could a clogged injector on bank 1 cause a lean condition on that bank and a rich condition on bank 2, while under load?
Never thought of that but it makes sense to me- the clogged injector could increase pressure causing more fuel delivery per pulse.
Thanks for your feedback man:-) still trying to trouble shoot my 06 chevy 4.8l. With your vid's and replys we have found broken wire on maf sensor, then tested o2 sensors by adding rich and lean conditions to both banks and found bad bank 1 sensor 1 (heat shield fell free and landed on o2 sensor and wore through a wire) still getting p0300 code, to the point it's misfiring so bad it can't get past 60km/h . At idle bank 1 FT's are +10 , bank 2 FT's are 1.3. Add throttle and bank 1 soars to high + and bank 2 drops to high - , it's a van, so not easy to work on, can't find a vacuum leak, so looking towards injector?
it can’t be a vacuum leak with those fuel trims. It does seem fuel related. Might also try swapping the O2 sensors and seeing if problem switches banks. If it does replace the O2’s. If the problem stays same then I would definitely suspect fuel issue. check fuel pressure on the rail at key on, idle, and 2500rpm.
Sounds like a good video lol.
Ok thanks. Yeah it would make for a great video, If my vehicle wasn't playing the starring role. LOL
Hey Matt, haven't had the chance to do fuel pressure test yet ( don't have proper gauge) got looking at down stream o2's and bank 1 varies 100-600mv and bank 2 800-900+ and both o2 STFT are locked at 99.2% ?
Matt on yesterday's TPS . I would like to say I don't subscribe to the phrase "the only stupid question is the one you don't ask". Unintended consequences during the test showed me there is no conductivity between a TPS and an IAC. While the TPS was disconnected am I correct to assume if you opened the throttle plate the IAC pintle would have closed and stalled the engine for lack of fuel. Also did the TPS have a ground at the sensor to the ECM provided and why did you need another ground ? I pay close attention to your vids because you do and say things to see if we're paying attention , one "C" in vacuum better not put a "E" LOL , so you have two options - 1 - I'm correct and 2 - I'm Nuts . 😜
Steve Rob Steve, based on other comments as well as yours I do need to revisit the cause of the engine speed increase with TPS and it will involve pulling IAC data. My thinking... which I agree may be wrong... is that the IAC is a non factor since presumably you would expect IAC to close if anything with increase in TPS, so I didn't consider it as reason for idle change. I though idle change was due strictly to fuel addition which of course I did not detect with fuel trims because I wanted to make it so ONLY the MAP and MAF could be used to detect the bad TPS signal.
Another analysis is in order to answer the question for sure and this is exactly the reason for my idea of "Schrodinger's Mailbox" where I can revisit stuff like this!
In part 5 I saw 7-8% LT, that dropped when you raised the RPM. Without watching all the parts, what was trim number at a steady 3000 rpm?
ScannerDanner Yes you are correct Paul, and it held steady BUT later on while driving it reverses and the LTFT's will be at zero but when I accelerate the FT's increase easily 10-20 sometimes more. The "vacuum leak" pattern happens only in the first 10 minutes after CL. The "fuel deficit" pattern happens later and stays consistent. But fuel pressure fine, cleaned MAF, no vacuum leaks confirmed by smoke test (which also confirmed no vacuum leaks). Both LTFT's adapt to variables in generic mode but bank 2 absolutely won't budge in enhanced mode at all- seems to draw a substituted value- but from where?
I enjoy the amount of knowledge I obtain from your videos, they've actually helped greatly getting my grandpa's truck running again. Favorite parts thought are you jokes about that Terd with lips scotty kilmore
Doing a injector balance test is defiantly the next test you should do. But I am going to go out on a limb and say that will not be your problem ! I think you are going to find a air leak in exhaust in bank one. And the o2 is working the way it should.
Holy crap this is precisely what I think. Verbatim.
I second this motion. Check the fuel injection system first. However I would take the exhaust leak test further. The car has an AIR system on it. I would check for leaks and check the components of the Air Injection Reaction System around bank one. I am not completely familiar with this system, but after looking at the AC Delco site. I think I see what could go wrong with the system.
Defiantly
What would be interesting is a person with a common problem and the ability to provide graphs as needed to provide you with ongoing requirements as required by yourself and then attempt to diagnose the problem.
Hello, not sure if you’ll respond but I’ve been learning a lot from you lately Thanks to your videos. I am getting bank 1 and 2 lean codes. While driving, my short fuel trims shoot up to 28-32% and go back down after letting off the accelerator. Starting to think I have a bad maf sensor. I’ve cleaned the maf sensor as well.
Its eiother a MAF issue or a fuel delivery issue. You need to check fuel pressure next
@@SchrodingersBox on it! Thank you! Do you offer live diagnostic services or have you considered? I would gladly pay to learn more you through video communication. Appreciate the knowledge every time 👍🏼
appreciated but no i just help through the comments.
definitely check fuel pressure next- you have to measure it at idle and under load.
@@SchrodingersBox will do, thank you
@@SchrodingersBox hello, checked fuel pressure and replaced the fuel pressure regulator. Fuel trims are close to zero now. Much better. Still getting lean conditions unfortunately. I checked my catalytic converter readings and I am not liking them. Pre cat sensors on both banks are reading normal (fluctuating up and down as they should), but my o2 sensors after the cats are not. Bank 1 o2 sensor 2 is stuck at .500 mv, bank 2 o2 sensor 2 is stuck at .100-.200 mv. Correct me if am wrong but aren’t both o2 sensors after the cats supposed to be at above .600-.700 mv? The weird part is that am not getting Cat deficiency codes. Only lean codes. Also shrt fuel trims keep climbing only when accelerating. They Settle back down to low single digits after decelerating or at idle.
Hello. Thanks for these videos. What is the answer of the last quiz? I suspect it is the O2 sensor. If I am right can you explain me why?
So what kind of glass packs do you have on your Fire Bird.
I had a '69 Tornado with duel exhaust and walker continental glass packs that sounded so mellow with that 455 cu. in. high compression engine under the hood. Last year they made that engine in a high compression model. So cool when the smoke would curled around the front fenders. That was a big step up from my Morris Minor.
I don’t use glass packs since I am maximizing performance. I lowered compression to 10.55:1 and put in a procharger supercharger with 9lbs of boost. The exhaust is a SLP Header and Y pipe combo with Borla exhaust. Absolutely zero backpressure even under load.
710 RWP at 5200RPM is the final dyno-tested result.
I am new to this and learning, I would look at testing fuel pressure and see if the pump is not working correctly. If the pump is weak wouldn't that effect all banks and injectors, unless one injector for bank one is clogged. O2 sensor would be what I think the issue is
correct on the fuel pump- it would affect all injectors. however we know the O2 sensor isn’t the issue because of the fuel trim response. it’s definitely not an O2 sensor issue.
@@SchrodingersBox
Could be a bad or clogged fuel injector causing the issue
No because we see no misfires or injector pulsewidth correction. keep watching to the end of series- it continues on another series. look in description on last video
Hi Matt, I like the game that you proposed, I would review the injectors bank 1, A shorted injector would do the O2 sensor will report lean.When we accelerate the amount of fuel is not sufficient and PCM open more time the injectors, because of this we see increases LTFT at banc 1. I think the problem with this car is a short injector, wiring fault or fault pcm signal to open a injector. Thanks for your class Matt,
What you describe is an open injector. A shorted injector will constantly dump fuel causing an extremely, extremely rich condition. But even so- if there was an open injector- you are right, there would be a lean condition on the bank due to the unburned oxygen HOWEVER the lean condition would be present even at idle AND there would be misfires every cycle and driveability problems. It is definitely not a shorted or open injector (which will be shown on the balance test) but it could definitely be unequal fuel delivery from an injector- i.e. partially clogged. However the fuel trims at WOT argue against that too. But your thinking is very accurate.
thanks for your reply, I'll watch the video again to try to detect the problem, thanks Master
I had an issue recently with my 2002 Holden Commodore which runs the 5.7 litre Chevy LS1 engine where I drove it after that it sat outside for a few days & had a hesitation when cold.
After I filled it up with fuel the next day the CEL display came on & the fuel trims Maxxed out at 25% on both banks,for whatever reason,my scan tool didn't read a lean fault code.
I tested the fuel pressure which was at 47 psi (it should be at about 60 psi) & the fuel pump was noisy.
I decided to replace both the fuel pump & regulator for just under $50 AUD (the whole fuel sender costs about $100 AUD on EBay),the regulator is a Buick park avenue one which I bought for $9.99 AUD,the pressure had to be adjusted in a bucket of fuel whilst running the engine,it was set at 61 psi which is the best I could do.
The fuel trims today were at 10.94% on both banks @ 100 km/h (60 mph) at cruise speed with an ambient temperature of 23 degrees Celsius & a coolant temperature of 100 degrees Celsius.
Fuel trim under load was at about 7 - 8 %.
So I'm glad that problem is all sorted out now.
..
thanks for all the great videos and all the different ways to look at them keep up the good work.
I'm looking at the graph. I truly believe it's the O2 sensor. I clean mine up just a little bit not too long ago. And then on day two it came back up only because I cleaned it, but I didn't use. Gasoline like they say you should use. I use brake cleaner to clean it off. But I will be doing a smoke test real quick. Just curiosity.
Based on your quiz questions, I would select bad O2 sensor, but why wouldn’t fuel injectors be a suspect here? Fuel pump and maf would affect both banks so those are out, but couldn’t fuel injectors also be a possible problem here?
I was Wright on both questions so it means I was a good student sir
If you’d lived close to me I’d give u two of my checks to diagnose my cars lolllll
Your a Diamond mechanic
thanks my friend but I would diagnose them for free!!
I'm actually very excited to find out the cause because I have similar problem with my Corolla :D. LTFT goes high under load. I have of course looked for simple and unlikely stuff like spark plugs, vacuum leaks and other leaks and did O2 response tests (was switching fine and did respond to lean and rich condition). Then I had my fuel pressure checked which was perfectly within specs. Then I took my injectors out and cleaned them (not much dirt came out) and spray pattern looked fine to me in all of them, so no much effect. I came to conclusion that my MAF was going bad and replaced it (of course I tried to clean it before). And it had a BIG effect on LTFT, dropped from +10 to 4 at idle and from +20 to 12 under load. But the characteristic is still there, so what the heck could still be the problem? Of course there was no way for me to measure fuel volume of injectors so they could still be potentially the issue. I also don't have any drivability issues, just a little higher fuel consumption.
And as for this Trans am case, I think the problem is with injector(s), maybe clogged/dirty.
Von Brontos We shall see! If your corolla was a 4-banger then all your diagnoses were valid, but if it was a 6-banger, hopefully now you see that much of the tests could have been ruled out.
Cleaning a MAF is a good idea anyway though- I do it every air filter change.
Schrodingers Box Yeah a 4-banger :P
your channel is great.. but i learned alot with Scottys channel as well... dont hate, plenty of room on the internet for multiple car fix channels
Just curious what you learned on scotty’s channel? I have yet to see one single useful EVIDENCE DRIVEN diagnostic information whatsoever. all I ever seen is parts cannon ridiculousness and “these computer controlled cars are crap- don’t bother with them” kind of stuff like you see in the automotive chat room forums from people clueless on technology and diagnostics.
The day I see him do a cam sensor bypass instead of throwing a cam sensor AND a crank sensor at a cam sensor code I think I’ll fall out of my chair.
yeah . i was kidding i find what you offer and how to explain is very useful and is not competitive for you . i have learned so much in this short period . thank you so much for this \ i am not very good in writing English . but i speak well / .
fuel trim at idle, STFT oscillations from -2.3 to + 2.3% and LTFT still at 0%! is this correct as a fuel correction? Thank you
ultimate focus RS MK2 NL kind of similar here, stft oscillating from 1.5 to about 3.0 and Ltft steady at 0, I know that seems a bit odd the ltft
Thank you for your very informative video bro👍👏
I have an Audi A6 2008.
Vehicle: Audi A6 C6 4F 2.0L TFSI 2008
(4 cylinders) only one bank.
Only P0171 no other codes.
System too lean at idle bank1
Freez frame DTC : P0171
Engine load : 20.8 %
MAF : Air flow rate. 3 g/s
RPM: 742
Fuel rai pressure: 688.92 psi
Short term fuel % trim : 3.125 %
Long term fuel % trim : 0. %
Fuel / Air ratio : 14.63 %
No apparent vacuum leaks.
Any idea, appreciated.
Cheers.
Nothing can be said about this data- there is no curve against load. You can neither suspect nor rule out anything from a freeze frame. All we can tell from this is it can't possibly be a vacuum leak and nothing more.
@@SchrodingersBox Thank you for the reply 🎉
Cheers.
Hi Bro, could you do examples of testing procedures on ASE A1? I subscribe and I always dig all of your content. If you read this question, please let me know! Thanks again for delivering outstanding content!!!
My next step would be a injector balance test.
Does your scan tool program show the duty cycles of the injectors?
It does show duty cycle, but we already know the duty cycle would be longer because of the high fuel trim. What are you suggesting I look at with the duty cycle that I'm not thinking of?
It would be interesting to see the duty cycle of each injector or even injector pulse width if your injector balance test shows a low flowing injector. Would the duty cycle or pulse width be higher than the other normally functioning injectors? It would be nice to see that type of evidence also.
Ah agreed. I need to check if I can get that. I may be wrong, but I belive that pulsewidth is set for all injectors on the same bank equally- i.e. there is not individual pulsewidth per cylinder- I don't know how the PCM could possibly know which cylinder to adjust pulsewidth for, especially considering no misfires which would be the only cylinder specific indicator I can think of. Makes sense, no?
I Enjoyed your video. I am trying to research the chemistry and mathematics of oxygen sensors so I can have a better understanding of sensor failure modes and how other problems will affect the sensor. There is a huge amount of misinformation out there . I having differculty working out what statements are correct and what is wrong. Would you consider doing a high level video on the reaction and how it relates to the platinum catylist and the electrolyte in the sensor.
I am considering it however there is, as you said, a lot of misinformation out there. My current understanding (ha! "Current", get it?) is that the O2 sensor measures the difference in O2 as compared to outside conditions- i.e. it ONLY measures oxygen. However other information some people are sending me (and it's from reliable sources) indicates that hydrocarbons themselves are measured by an O2 sensor. In other words, I would say a rich condition is measured by the absence of oxygen, or in case of too much fuel "the fuel displaces the oxygen lowering the oxygen concentration" if you follow. But, what others are saying is that I am wrong about that and the O2 sensor is indeed measuring the additional hydrocarbons directly. I need to do more research to find out which is accurate and of course come up with an experiment to prove it.
From the info I found the electrolyte moves spare O- that comes from a reaction of O2 with H2 (assumed to be unburnt fuel) and CO . Thus the O- creates a -ve charge on the exhaust side and a positive charge on the reference side. Therefore it is actually a "can further combustion take place" sensor. I will post a link to a paper on it.
My first guess would be an exhaust leak causing the long term fuel trim to go lean overtime. I think this because you're not having any driveability problems. Briefly clog the exhaust while checking for leaks. Is the 02 sensor bias rich a bit on that bank? My second guess would be partially clogged injector causing a lean condition I just think you would notice it somewhat under load. Doing the injector balance test would be good to eliminate this.
We are in total agreement James- thanks for the comment, I believe this is your first on the channel. In dact, I was going to put my money on an exhaust leak until the video i just released today.
At his point I would rule out a vacuum leak because during a load the largest amount of air is metered air and a vacuum leak would be a minor contributor to the problem.
I would listen to the injectors for inconsistent sounds comming from one, perhaps with a screw driver used to convey the sound. I would check the voltage on each pin of the injectors relative to computer ground for consistent voltage difference between pins of each injector by back probing the electrical connector. checking for less current draw inside the injector due to high resistance electrical connections or internal failure.
These I would test in an effort to discover which injector might be delivering deficient fuel quantity.
According to your rules of the game, the answer was c. Chevy don't work the same as the "other car" ;P For the first question.
Hey @Schrodingers Box I have a terrible experience. I drive 07 Honda CRV 2.0l (Stick/Manual) than lacks power. When I floor it on the road, the car doesn't react to it. But when you pull your leg off the pedal, just before your leg is off the pedal power kicks in. So by deduction, when you lightly touch the pedal, power response. I took the car to a dealer for scanning, first I got a code that AF sensor failure, changed that. They later suspected PCV Valve that was ok. No more codes. Injectors work fine. Fuel pressure ok. Where can I go to look next?
What data do you have? Always start with basic data
@@SchrodingersBox at 2300RMP, STFT-0.04% and LTFT-1.6%
What is the TPS voltage at idle and at WOT?
@@SchrodingersBox It says 73%. Hold on I'll go for scanning tomorrow for voltage.
@@SchrodingersBox It's 8PM here in South Africa.
I got it right! So in tradition on this channel I will gloat and be full of myself!
No- you GUESSED it right. When you actually understand what I am doing then we will talk about your acceptable behavior. But not a minute before then.
Swap o2 sensors around see if it switches banks
hello Matt. if a car has high STFTs and maxed LTFTs that stay the same with throttle, is it correct that there is not a vacuum leak or a fuel delivery issue? perhaps upstream O2 sensor
correct
@@SchrodingersBox thank you matt. i had a lean code that got worse with throttle that ended up being my fuel pump, but it didn’t fully fix the lean condition. going to attempt to diagnose the wideband AFR sensors since theres 2 and one bank is showing ever so slightly leaner
yep you either have a pegged rich O2 sensor OR a legitimate extraneous fuel source present in the engine.
@@SchrodingersBox extraneous fuel source being like a stuck/ leaky injector?
Could be that, or overreported induction or a PCV issue.
It’s either too much fuel or too little air OR the perception of one or the other by the PCM
10:41 That don't make no god damn sense! Had to replay that a couple times. The more I watched it the more I laughed until I cried. Hilarious!
***** I replayed it 4 times lol
Good video. I have a p0171 code on my nissan. At idle 800rpm, Short FT -20% and Long FT 13.3%. When at 3000rpm, Short FT fluctuates 0-3.1% and Long FT 3.1%. What could be the possible reason for this?
Dear Sir,I have a BMW E46 316ci .The fuel pressure was damaged ,so low fuel pressure ,so high LTFT (+20,3).After replacement the LTFT is remaining +20,3 but the STFT is -20,3.My question is how long it takes the LTFT to become close to zero in order to drive STFT close to zero? Thanks in advance.
one tech to another, I like your OCD! vacuum! my man.
Good video. I'm thinking fuel delivery problem(fuel injector/s) on bank 1. Since LTFT is a learned value you will not see the O2 drop lean. The O2 seems to react pretty normal at idle so I dont see a problem there..
A injector leak down/flow test or swap injectors, depending on whats easiest.
SpelFocus Agreed! It will definitely be one the next tests and for exactly the reasons you mentioned. Welcome to the 2% lol!
Schrodingers Box I have another suggestion, It would be interesting to watch Mode 6 data. I don't know if Pontiac have misfire data but I say its worth a look. So what I'm going for is to see if the computer can detect any misfire and which cylinder/s. You may have to clear the FT memory to have best chance of see anything.
SpelFocus I do have misfire data- no misfires even under load but I forgot to show that in the video.
if your there i have good question i think. Have you ever taken an exhaust off to do a transmission perhaps. And when you were all done you had a system too lean. fuel trim suggest its a vacuum leak. how would i eliminate an exhaust leak?
Can’t think of a time i didn’t have to remove an exhaust to do a transmission. a standard part of the R&R.
Usually i just soap water test for exhaust leaks.
Is there any way a tps sensor (located on the fuel intake.) could be a part of all this?
I don’t follow-I consider a TPS to be a Throttle Position Sensor. what sensor located on the fuel intake is called a TPS?
Hi Smith. Thanks for the good work. Please tell me about the TOAD Master scan.Thanks.
Not familiar with that one sorry. Thanks for watching though
One question hitting all the time on my mind is that if a code is lean mixture why fuel trims are positive? Because positive fuel trims means ECM is adding fuel. And negative fuel trims means ECM subtracting fuel trim. Am I right?
That’s correct. In a lean condition fuel trims will be positive because it reflects an addition of fuel.
if the 02 sensors are reading rich which means theres too much fuel it excludes bad fuel pump/low fuel pressure. but if the maf sensor is bad it can trick the fuel system into thinking theres too much air which will cause a rich mixture and both o2 sensors stuck on a rich condition. does that sound correct?
Haroon Ali It is indeed correct except that we can rule out MAF in this case because the car is only lean on one bank and the MAF would equally affect both banks.
Schrodingers Box i thought you said both O2 sensors went rich on WOT? 20:06
Yes I did but we are looking at a lean condition on one bank under load as our problem. Rich on both banks at WOT is normal if anything that confirms 100% it cannot be a dirty MAF. For the reasons you mentioned- if there was a MAF problem where more air was coming in than being measured, we would see lean on both banks at WOT. I recommend watching my fuel trims video Haroon as it also explains MAF sensor as well as fuel trim.
2007 GMC Yukon 5.3L Engine: I get a P0171 code when running the engine with the AC on for about 20-30 minutes. Vehicle begins to jerk and shake on idle. After the vehicle cools of or I turn off the AC, it eventually returns to normal function. Any ideas?
what data do you have?
One more thing sir, if we press gas pedal down a very little, in idle, the system will shift from Closed Loop to Open Loop.
yes that’s because the system is going into open loop since it cannot control the closed loop variables. it’s called “open loop 3 mode”.
I'm having issues with an 08 C6 LS7 swapped in a first gen. Lean condition on bank 1. 24 to 25% fuel positive trims at idle up to 1200 rpm goes away at 1300+. Watched all your fuel tr videos and co vince'se it was an intake or vacuum leak. However using carb clean or water sprayed on intake and injector pockets I get no increase in throttle or sound .
Where next
it’s a vacuum leak. on those engines it often leaks in a the valley between the heads. a smoke test would easily show it
So are you staying a vacuum leak in the actual valley cover? I did replace the intake gasket after the spray carb choke cleaner around the top side of intake and all injectors produced nothing.
I'll look into smoke test
Hi Matt, I see the video again and I have a new theory, It's possible the car has an injector dirty?, We have a problem with the fuel pressure in bank 1, the fuel pump and regulator fuel are common to both bank, but the injectors are individual for each bank. I think an injector is dirty in bank 1 or the injector has a voltage drop by a bad connection and not open enough. When accelerate there is not enough fuel for a stoichiometric mixture and PCM prolongs the opening of the injector. Thanks for this exercise Master.
Indeed! Manolo! Many people agree with your dirty injector theory for exactly the reasons you stated! We will find out in a week or so!
Ok Matt, thanks and congratulations for your channel.
Nice video, thanks!
In my car I don't see any error codes yet but the following tests always failing
MID:$70 TID:$01
Rich to Lean sensor threshold voltage(constant) -
Max: 450.63% Min: 61.78%
Test result value: 655.20001%
FAIL
----
MID:$81 TID:$19
- Fuel System Monitor Bank 1
Max: 4 Min: 24,657
Test result value: 6,528
FAIL
----
Where do you think I should start ?
+Osama Altobuli Sorry I would need these translated to voltages and %'s that I am familiar with to help.
I have a very odd issue with my 05 Nissan Pathfinder SE off road v6 4L. I had the p0171 code, but for some reason, it only trips at load after warm up. Something seems to click on, and I can watch the live data just start running up to 25% and staying there until it cools down and is restarted hours later, when it goes back to correcting the fuel trims. Also, the bank 2 sensor 1 goes up to .9v and stays there rich on bank two, so I'm not sure why this happens in conjunction with a lean bank one unless there is a manifold leak on the bank 1 side and all that extra fuel is still registered on the bank two (I swapped out this a/f sensor and captured the same exact readings for both sensors, which also means the old factory one I put back in it is probably still good). I've been putting off ripping into the exhaust manifold in fear of stripping something out without having the proper tap and dies to bail me out. I might lube it up and gradually give it a go and at least see if I can find any leaks hooking up my vacume to the tail pipe. Lol jk vacuum. Sorry, I couldn't resist 😹. I just don't understand why it only occurs under load. Could I collapse a hose or something, or when the fan kicks on or some switch activates it disrupts the O2 sensor signal somehow tricking the computer. Idk. Is there a load switch or something that would just all of a sudden cause the one side of the engine to go lean and the other side to be normal.
This is a pretty tough one! Of course, being the cheapskate that I am, if the there is no drive-ability problem, (which you have ascertained that you don't have,) I will be shopping for black electrical tape over the check engine light:-) Given the O2 traces at WOT, it is obvious that both banks are being controlled properly by ECM. I would be interested to see how the LTFT is trending towards the high value e.g. reset and watch. Is it drifting towards the higher value or reaching it pretty quickly? If the ECM had capability of being able to control the fuel trims up to 50%, would this be even an issue? LTFT is there to account for general wear and tear. Of course, we want to know what would cause one bank to need that extra positive LTFT? I can understand one clogged injector but the car is behaving as if one bank is needing consistently more fuel than the other. How is the EGR plumbing on this vehicle? Is it possible that problems in the EGR flow would affect one cylinder lot more than the other?
I do remember this engine having some bizarre issue which turned out to be clutch switch or something like that from your early video. I got hooked on to your channel from that video. I have not gone back to see if the previous problem was similar or not.
I like the idea of EGR plumbing but it feeds to the intake right behind MAF so it would necessarily affect both banks... though, come to think about it, the EGR is sourced from each exhaust manifold so there is potential for a leak on one manifold connection. Hmmmmmm.
CPS can be ruled out because it would affect both banks since it causes anticipated fuel adjustment.
Is it possible in a map system to have a vacuum leak but not raised rpm at idle?
Not initially. but the IAC can certainly adjust idle later.
I have a lean code I’ve been trying to diagnose for a while now. Your videos have been very helpful but I still can’t pinpoint the problem. My fuel trims are fine at idle but but my LTFT jump up to 40% under load. My freeze frame shows usually at 2k rpm. Cleaned my MAF, inspected and changed my fuel filter, cleaned my injectors code still was there. Checked for Vac leaks for the hell of it and nothing. Inspected my TPS and noticed it was out of range so I recalibrated it. Changed the cats because they were 15 years old and the O2 sensors. Changed my injectors along with fuel pressure damper, and my fuel pressure regulator along with my fuel pump because I have a spare. I want to test my throttle body motor and APP sensor because I know they all feed into my fuel trims. Is that a good next step? Any information on how to test these? Any help would be appreciated.
You have to test fuel pressure and look for a rich response from o2’s under wide open throttle while driving
i will go after injector balance test and check the o2 sensor not mass air flow sensor or vacuum leak for the reason of this last two will affect both bank at same time with same readings on fuel trims
+Luis Baez If I recall I thought the same and indeed do that later in the series. Good thinking!
these videos are amazing!
I don't know what to say, you are just a professor!
AT IDLE STFT IS OSCILLATING FROM -0.8 to 1.6
LTFT STUCK AT 24.2 when I increase the rpm to 2000+ LTFT Goes down to normal. Vacuum leak?
Yep
@@SchrodingersBox thank you for the quick reply !