As a mechanic, ive sat in auto dealerships waiting to pick up a part at the parts dept and listened to the service desk presenting lists of "repairs" to poor unsuspecting souls..hearing the diagnosis and the parts and labor pricing is almost painful at times becuz i know what the real time involved for the work done should be and i know what the parts pricing should roughly be... its so sad... people are being fleeced alive, especially old people and women....these shops take full advantage of people ignorance and their helplessness to to their own repairs....integrity and ethics are often absent in this field.
it comes from being continuously in contact with humans that know ZERO about how cars work, the frequent " my car won't start , I think the starter is bad..." mechanic finds it was a burnt fuse, being honest will put maybe $ 20-30 bucks in his pocket, or letting the customer believe he was right, And charging him for the new starter,( which goes straight into his pocket cuz the old one works great and is already installed) ,and the imaginary 3 hours of shop rate in labor to install the imaginary starter, the customer's happy to pay it, and $30 for honesty , vs. $400 -600 for nothing........ they get used to easy money, and in time burn anyone and everyone... I think all mechanics should have three random repairs every 5 years, that are actually employees of the BAR, who bring in cars with issues , pre determined, and report on the mechanics, ability, how he went about diagnosing cause of issue, did more charges than needed appear on the bill, did any of the loose 1 & 5 dollar bills stuffed in the cupholder disappear, or the gold chain half hidden by drivers floor mat? I just got ripped off by a mechanic who quoted 3 estimates...$500 to get it to run better, $800 to be able to get on the freeway, and $1200 for everything to work right...one mechanic didn't clue in his partner what I was quoted, and when I brought the car in the next day ( having no other option)only the partner was there, I had to ask him , if there wasn't usually something I signed , that had a price and what needed to be repaired? He then asked me what the other guy quoted me....& hastily wrote $500 when he saw the look on my face....I came back to my car having the same exact issues, returning to them, then he told me the ECU needed to be replaced...and he had already ordered it, but wouldn't arrive for 2 days....so I went and got the exact same ECU and brought it to him ,but he now couldn't program it , and sente to his locksmith buddy who did it in 5 minutes, and charged me $300....I did a throte relearn, and the car ran exactly the same...same issues, no change... $500 for vague wiring repairs $65 for diagnostic/engine trouble code printout, which told him the same that I did when I brought the car, $140 for tested used ECU, and $300 to program it......$1000 later, and I'm the same exact place I was before... I'm going to his shop tomorrow, and I'm so pissed off, I can barely see straight...my Nissan buddy finally gets back to me, so I ask him why would mechanic tell me he found the problem, make the repair, release the car to me only after payment, the problem not be fixed and then state he found the real cause of the problem... "To take your money" , my buddy says...... what do I do next?
Does California Automotive Repair Act , permit a customer blatantly ripped off, to pummel the crooked mechanic until he agrees to fix it right, and right now?
I absolutely love your shop policy, more shops need to implement this policy: If you are unable to fix the problem, the parts come out of your pocket. There are too many mechanics out there who just throw parts at a car and pray that it fixes the problem. Good to see techs out there who value the customer's time and money.
I cannot remember how many times I have paid for parts that were not broken. Sir you are a breath of fresh air. Finally I find a mechanic who does not shotgun a problem with parts until the problem goes away.
Many thanks my friend. Indeed buying parts should be the result of the diagnosis, not the method of it. But it takes knowledge of systems to do the diagnosis and I appreciate the few people like you who are willing to dedicate time and effort to that. In fact it is exactly why I made this channel.
And the award for world's best mechanic and most stand up person goes to: this guy. Also I really appreciate the fact that you were going to buy the part for her if you were wrong about it
I agree, I am just a backwater mechanic, but I find so many people don't have the slightest clue, even the one's that do this for a living. You have the skill, just figure out what's not causing it, and test to see what it is. I laughed at the frozen piston part. Good job, we need more like you that know how to look outside the box.
@Matt, all of those issues I have been having with my 01 S-10 4.3L were because of a clogged pre-cat, and it blew out the back half of it into the primary cat. Recently, the vehicle would hardly get out of its own way, and on the road it wouldn't accelerate for $hit!! Other than the obvious symptoms, I used an infrared temp gun, and the temp at the back of the pre-cat was 150* lower. The engine was bucking, fuel trims were very lean, was throwing a P0101 code, P0300/P0304 code(s), burning excessive fuel, etc. Also the post cat O2 was almost pegged out at 0.85 volts constantly. Took it to an exhaust shop where they did the same back pressure test, and at 2500 RPMs, it was almost 6 psi. They replaced both the pre and main cat with just one cat, and now the truck runs great!! Several misfiring incidents over the past several years (corrected now) led to the cats being destroyed. Hope this is helpful info to anyone that watches (and should be!!) watching your channel.
This channel is addictive 😅 one day a fuel trim video popped up and ever since is a non stopping thing I watch at work, during lunch and even before going to sleep.
Hi, I would consider it pretty normal that the vacuum gauge reads 0 when you try to rev it with a clogged exhaust. In normal operation, intake vacuum is maintained by air flowing in being restricted by the throttle valve. If the restriction is elsewhere, the pressure difference will be elsewhere too. In this case the idle vacuum was already extremely low, which indicates a problem right away. Vacuum gauge can also be helpful in diagnosing a burnt intake valve. Average vacuum will be almost normal, but the gauge will flutter synchronously with the engine speed once per 2 revolutions. In fact I consider the vacuum meter as a very useful tool, but as with all tools it takes some explanation and practice to be used effectively.
Yeah, your right how dare people make money from your ignorance of mechanical knowledge. They should just have a free service for people who need love and their car fixed... all free, yeah that's how it should be.
findvoltage well there is actually ignorant mechanics that try to solve problems with improper diagnostics, and that’s when they “want money”. She’s obviously not talking about all mechanics, which is why he said WE WANT MECHANICS LIKE HIM. you’re a dumb ass 😂
findvoltage I mind when mechanics make money from their mechanical ignorance...don’t mind one bit if they make money from my ignorance! To boot they’ll fuck up something else _as in this video_ Ill recommend watching it 🤪
exactly! "Actions speak louder than words!" Too many people that dress like and try to sound like Pros dont come up to your ankle 🤗 After replacing melted catalytic converter the key to ensure the replacement won't melt in short order... I guess "old lady" drove ignoring CEL caused by old plugs.
It's sad that there are people who say they are "certified" and can't even diagnose a problem. This is exactly why i'd prefer to do the work/diagnoses my self with the help of youtube of course. keep on keepin' on. Your video's are great btw, and have helped me a great deal. thanx
I know this is an older video but I am constantly amazed at how very few people see the value of a vacuum gauge as a diagnostic tool. I have just diagnosed the very same issue on a Mazda Tribute v6, like most others, the first thing I turned to was the scan tool expecting to see everything pointing to lack of fuel. Surprisingly, upstream O2 sensor was cycling and fuel trims were within the realms of normal. Next hook up for me was a vacuum gauge as I was already suspecting an exhaust restriction. I got exactly the same response as you did, lower than normal vacuum at idle and very low, near zero at revs. I have seen this many times before in my 40 plus years in the trade, it pretty much confirms a blocked exhaust. I am in an industrial area so I dropped the exhaust, first after the cat, no difference, then before the cat and the vehicle was able to rev freely. First problem solved, now to find out what caused it. :-)
In this application, the gauge was able to give some unscientific indication to support a restriction hypothesis, but it was the backpressure test using the vacuum gauge, not the vacuum test, which ultimately gave the scientific validation. Seeing as how lower vacuum occurs at open throttle, it should be apparent the scientific application of a vacuum gauge is invalidated for this test due to lack of an independent variable. As you also indicated the fuel trims in modern vehicles also completely invalidate ANY application of a vacuum guage in modern engines. For the vast majority of diagnostics in OBD2, a vacuum gauge is useless in scientific methodology. In fact I even having a video showing how the PCM's stoichiometric adjustment even fools the gauge into indicating there is no problem despite an obvious issue being present.
I can tell your a good mechanic because your not afraid to say 'I'm not sure' or read some directions off a rarely used tool. The ones who know everything and are always right waste so much time and often other people's money trying to prove it so. And your rational mind lends itself to problem solving.
Funny as soon as you talked about the systems of this car, I said it had an exhaust restriction. I am a very old mechanic and back in the early 70's GM had a very bad exhaust problem. They had a double walled exhaust pipe before the muffler for those who don't know where the exhaust pipe is. Anyway when the car got hot and it was raining and you went through a puddle and hit water onto this pipe it collapsed but only on the inside. If you looked at the pipe it looked fine from the outside but the car didn't go over 25 MPH. After the first 2 I diagnosed the problems in less than 1 minute. No power, hissing noise under the car either moving or not, just trying to rev the engine. Now the vacuum gage is another tell of this problem and will accurately diagnose this problem every time. But after cats came out I found both a clogged cat and a broken apart cat with the insides stuck in the muffler clogging the exhaust. But you are right after you fix this problem you need to find out what caused the cat to go bad.
I was quite surprised to see that the vacuum gauge worked to identify the backpressure on a PCM equipped car. In the days prior to PCMs, I used a vacuum gauge quite often to diagnose engines. Before the days of scan tools, it was an excellent means of diagnosing ignition timing problems, fuel mixture issues, vacuum leaks, sticking valves, and exhaust back pressure. However, in cars with a PCM, the PCM can make changes much faster that the vacuum gauge can read, and have mostly rendered the vacuum gauge useless. My old vacuum gauge sits in a tool box with my dwell meter. Museum pieces. I am a Trans Am guy like you, and my one experience with a clogged exhaust happened on my 1976 Trans Am in the early 80s. I was driving home from Florida to North Carolina when the car lost power. I couldn't go faster than 40 mph and the engine overheated at any speed over 30 mph. On the side of the road I used my vacuum gauge and got the same results you got, indicating a clogged exhaust system. The 76 Trans Am had a different kind of catalytic convertor than the modern ones in that it was filled with catalytic beads. There was a screw on cap on the bottom of the catalytic convertor that I could remove with an Allen wrench to cleared the beads out of the convertor. Fortunately I got enough beads out of the convertor so that I could make a normal drive the rest of the way home where I installed a bypass pipe in the place of the convertor. In the 80s leaded gas was cheaper and more available then unleaded, so I would run leaded gas in the car. I believe the leaded gas had fused the beads together, which created the blockage.
Totally agree with you. One way you can tell a "mechanic" doesn't know what they are doing is they use a vacuum gauge on a modern car. Actually to be honest, most people who used them on older cars stuill just guessed anyway because the results are subjective. The exception however is with what I did in this video and using the PRESSURE gauge on the exhaust. Regardless of the car's design- a clogged exhaust WILL increase backpressure and the car cannot make adjustment for it. You WILL see backpressure. So in this case the vacuum gauge is reliable. ALso- yes, absolutely (no pun intended) you could also use MAP and see there is excessive pressure in the intake manifold. You can also see it through the DPFE on Ford vehicles as well. Great comment and question.
Dude , I can't thank you enough for sharing your knowledge on diagnostics. I'm subbed to your channel and can't stop watching. I'm not a professional mechanic, but lovee to turn wrenches on my own stuff along with family. You have helped give me arsenal of weapons for diagnostics. Actually chasing a very similar issue. Had thought it was vacuum, or 02. Changed the O2 's because the car sat for years and noticed some material on the b2s2. Any how , I'm off to a vacuum test!!! Thank you for saving my money !!!!!!
What I really like about you Matt, that you don't stop at changing the faulty part (in this case the clogged cat converter), but you wanna find out what caused that issue at the first place. Even if the customer doesn't want to fix the main problem yet. At least now s/he knows about it. I've never seen a mechanic like that. Absolutely AWESOME you are!!!
The vacuum gauge has turned into a tool of the past. Good to see it used here. The vacuum gauge was very useful to me as a young mechanic working in a high volume trans shop for 5 years just out of high school in the early 80's. Back then on GM and Ford, no vacuum= very late or no upshift at all out of first. Back then, engine vacuum was like a "load sensor" for the trans, along with the kick down cable or lever. I recently used my gauge as a quick way to verify good engine vacuum at idle after replacing upper intake gaskets on my 96 Ford explorer. On the car in the video, I would bet that your vacuum is higher at idle after the repair. 10 inches is too low at idle on any car. If you are not higher than about 17 at idle you know something is wrong.
I just got one with a plugged exhaust. But the service writer said to put coils and plugs in the misfire history cylinders. Its not always the mechanic but most of the time it is. The trick now is to figure how to determine exactly which one and how many. It has three. Thanks for the tip about the clogged muffler. Keep up the good work. people need to see honest techs with some good knowledge. My back pressure test blew my hose of my gauge,lol
WOW!!!! I am having a similar problem with my 95 suburban, I am no mechanic but I have been fixing my own vehicles for 40 plus years. I also noticed the "sound" when I accelerated. Everyone I asked never noticed any peculiar sound! A couple of these people were mechanics. Up until I watched your video I thought I was over analyzing the situation, as is often the case with me. (I'm an Aquarius with ADD and OCD. Yeah) So thank you for the video it was well done and very informative!!
One of the best mec and well explained videos ever seen on UA-cam this guy is super smart and have plenty of knowledge on fixing and finding car mec issues
This old video is great. One thing I learned is clogged cats get really hot. You can diagnose a clogged cat with an infrared temperature laser, ingress and egress pipes, or benchmark in your journal what a normal temp cat would be at, and then take a temperature reading. other videos describe this. Also the exhaust coming out of the pipe will be super hot.
Thanks for posting this great video.I do work as a certified mechanic on daily basis,but i must say that i am impressed and grateful for these videos...it shows that everyday you got too learn something New..or at least update yourself.....To understand how it Works and too be interested in solving the problem.One of the better videos i have seen on you tube that involves diagnostic on cars and a better understanding on how too think.....before you change a part on a vehicle..Thanks again for making the car World a better Place. Greetings Fredd from Norway
You are a Jedi Mechanic! May I be your padiwan.... honestly you make understanding mechanics incredibly easy. I learn so much every video I watch. Thank you
Good thing that the poor lady found you! I agree with ur diagnosis bro, its amazing all the "pros" didnt catch it! It was pretty obvious and well verified by ur tests.. one thing though, yes it may be the catalytic, but swapping a new one in there may yeild a temporary fix, as cats go bad for a reason! and the Cause of the original getting plugged up needs to be addressed or the new one will end up the same way down the line...Ive had new magnaflow cat melt the honeycomb and seen it crumbled inside after 6 months of use... im sure you already are checking into the cause... great vid
No mechanics like this where I'm at. I currently have a vw cc acting the same way and fortunately caught the guy who put an secondary air pump on it was just going to parts change all over that engine before he ever got to the problem. Sadly I think he knew what it was but hey its 2020 and this year has truly changed people for the worse. I did yank the car from him but not before he removed a perfectly good part and replaced it with a $505.00 part. He literally told me he needed to replace every link in the chain of parts he believed was causing the problem. Told him no and took my car back home. Now it has been diagnosed with a back pressure exhaust issue in addition to a 1 plug and 1 coil replacement. $1958.00 estimate. I have done my own research and was able to find all the parts for 600.00 and will be doing it myself.
An almost unbelievable diagnostic(?)approach history in this poor woman's quest to have her car operate normal. I have witnessed over the years several other technicians with the same modus operandi to make maximum financial gain by using the very least amount of time and effort. The sad part is that they released the car back to her in the same or even worse condition that it was presented to them in the first place.Thank God she was led to you Matt.
+John Kimmel I see it allllll the time, unfortunately. All the time. In fact, it got to be so friggin frustrating I decided to make a UA-cam channel a couple years ago to fight against this and empower the DIY to be more defensive.
I check my PM's and you never left your number. If you PM me with YOUR number I'll be happy to call. I leave town again on Sunday afternoon so if I don't get in contact before then I won't be able to help.
You, my friend, are amazing I am hooked on your videos I have an RV with a ford engine.giving me the lean codes that you talk about Been to FOUR mechanics. Yes, parts replaced but error codes still come on. After there cleared, they come on usually a after fifty miles of driving After watching your videos, I am going to try troubleshooting myself Thanks for your excellent videos
Really appreciated your intelligence approach . After watching your video my mind is turned back to my Toyota Yaris 1.0L 2000 model old car probably old issue lack ok power forces to paddle reach to 100+ km/h buzzing sound while accelerating fast, LTFT +1.5 at idle , check exhaust seal was ok no cat converter in model , decided to check engine compression and found 3 of spark plugs found oil deposits coil plugged side , that’s was the issue leaks spark plugs seals , got a serviced well tighten well, wow amazing improvement LTFT exact on 0 in idle , it’s all created to you sir the core knowledge way you teaching ❤
I have had this p0420 code on my 2.4L '09 Camry for 3 to 4 months now. MPG and performance has been optimal the entire time. Oxygen sensors are new, exhaust is new, maf new, air, injectors...but not the cat. Everything passed the health check on the Techstream diagnostic report except the catalytic converter p420.... I tried 'cataclean' and high-rev driving 4000-5000 rpm for about 50 miles a week ago (heard this helps clean the cat, makes sense) and this all improved the engine performance, but did not clear the code. I drove the car home from work yesterday (performance was still flawless even at high (5000-6000) revs, inclines, shifting etc). The next time I drove it was today. it was pouring rain and had been pouring rain all night (maybe, maybe not relevant). After letting it warm up in the rain 5-min I engaged the gas and immediately there is harsh shaking, blinking cel for p0420 and p302 misfire I've never experienced. I thought perhaps something electronic got wet from rain? But, even after I did a soft-reset of ECU the symptoms, shaking, and blinking CEL p0420 returned... there was also a strange smell (not quite rotten eggs, but definitely unpleasant). I examined the exhaust leaving tailpipe. There were half-second bursts of pressure & then no pressure which seemed in sync with the shakes of the car. Not even a mile from home, decided to take the spare Yaris to work; didn't want to cause more damage... Do you think it is most likely the catalytic converter? Is it often for a cat to go that bad that fast? From no drivability/performance effects to completely catastrophic overnight? I thought a dying cat was supposed to be a gradual worsening...? [Remiss of me not to mention the engine has 360,000 miles w/ original cat and transmission, but I have no problem replacing the cat myself with $250 one off amazon. I knew the day would come; just thought I'd see it coming over a longer period of time.]
Thank you! You covered all the possible symptoms for restricted air flow. I am almost sure now the cat is the culprit to my problem. This was very helpful and I just subscribed. I'm now apart of the 2 percenters club.
We have a 2012 Mazda 6 in the shop now. No codes. occasionally throws a 0420 code with a note about warmup. the hissing kind of sucking kind of vaccum cleaner with out the motor sound is remarkable. Later today I will wander under it to see where exactly the restriction is. On newer cars that use a 14mm fitting for the 02 sensor you can you a Dorman Spark plug non fouler to create your "bung hole" fitting. Great video. Nice to see good guys (and little old ladies) winning one.
Good job SC. Hear is one for you. I had a 2008 F150 with a 5.4l V8. vehicle showed multiple miss fires and my friend attempted to fix with just adding 1 coil. He immediately gave up and brought to me because he did not want to mess with the plugs if you know what I mean. How ever I verified the miss fires and replaced all over plug coils and plugs after finding more than 3 faulty coils and plugs with almost no electrode. Past experience shows that when one or more go bad the rest are not far behind. Anyway after repair the truck ran rough, had no power and bogged down however you could slowly get it to gain speed if you where feather light on the pedal. I immediately knew it was a restricted exhaust. This truck has 2 cats one for each bank. Now I did test vacuum and my reading was normal 22-25 in/mhg and steady so you would think it should be low. Tested pressure before cats, pass side 2 psi at idle, 5 psi @ 2500 RPM as manufacture test procedures, driver side needle would just bounce from 4 to 10 psi and peg at 10 at 2500 RPM. Ford test specs for this truck or engine are 4 psi at 2500 RPM as ok. I also put a scanner on this truck and monitored live stream and O2 sensors normal and changing lean-rich as normal with short & long fuel trim with in range. I just wanted to Pass on that in your video you stated that anything over 2 psi is a restriction I just think that you should have them refer to manufactures testing data results instead because, 2 psi might fit a good number of vehicles just not all. My friend told he drove the truck before any repairs on a trip for a long distance and it ran with missing and pinging and lost power over weeks.
07 f150 5.4 Triton,40k mi., 8 miles to the gallon, low power, smells like sulfur, , makes a waaa noise when accelerating, no codes, mechanic put it on some sort of cheap scan tool no problems found Should I go somewhere with a more sophisticated scan tool for Fords ?does anybody know what these more sophisticated scan machines are called for Fords? Maybe I should get the cats checked, Ford technician said to check for falling/failing BARO pid. Any tips of the day from anybody would be appreciated
+steven lesher Drop cats at manifold and drive to see if power gains come back sounds and smells like bad cats. now when you do this if you have not already the cats wont drop all the way down but will work. if you use a pressure gauge in place of dropping cats ford says max 4-6 psi but you should see almost none. Cause is usually cylinder misfires on one side usually the affected side. the codes wont set a hard code until the problem occurs for a specific amount of time which will turn on the check engine light. however it will reset if the problem goes away for so many key starts. hope that helps if you have not already fixed.
+DE Nichols thank you for the reply. I can give you a little bit of other knowledge on the checking back pressure on the exhaust if you care to know. You can use a dedicated exhaust back pressure gauge but if money limited you can use a vac/pressure gauge. Just make sure the hose is long enough to reach into your hand while sitting in the vehicle and for reasons is so you can see the gauge while you test and for the most important so you do not burn the gauge with super heated exhaust gases and burning your hand, however you cant test for like an 1/2 hour the hot gases will surely heat the gauge and burn your hand do to conduction and radiant heat. I found an brass adapter with a barbed end at the auto store or homedepot / lowes to match the threads of the O2 sensor and used a fuel line with clamp reduced the hose down with smaller diamiter hose to fit vac/pressure gauge hose. just remember you only need a few minutes if that to see if pressure rises at idle and at high RPM. You can also check engine vac with the same gauge to anchor your diagnosis as a double verification.
Well I'll be dammed.... I think I finally found a person that would make me feel like im working with myself... ladies and gentlemen I am far too humbled to be saying this with pride or self centeredness... I'm just speaking my truth. I have felt like there was something very wrong with my style of work. I've been told that I'm a technical freak and a complete overkill. I've been told that I'm a bad mechanic because I act like an "elitist". But I keep to myself verbally and I just do my work....I dont make others feel badly and certainly don't try to make others LOOK badly. God works in funny ways to have my stumble across this video when I wasthinking of abandoning my trade. But this is really how my call to action was meant to be. The best I can be. Thanks for sharing your skills and knowledge of a higher order
Hi. I have Datsun Go, 1200 cc petrol engine. My car recently involved in a car accident. It crash the back of an old car which happen to have stronger body tham my car. So the front of my car is wrecked. I have fixed it. But after 100 km the car loses its power. Seems like the throttle can not reach its maximum power. It stopped at half of the digital indicator. What do you think probably cause it? I ask local repair shop (not doing any test yet) they say "the throttle sensor" cause it. I have spent a lot of money to fix the car after the crash. Please help me to decide what to do next. I dont have much money left :(
Schrodingers Box I am not sure what it means. Because the difference of our language. But I will translate it and give you the update. Thank you for give your time to answer my question. Thats mean a lot.
sometimes ignition wires do fix the problem. usually that would cause i misfire and the car will run much worse when you put the engine under a load, and when the weather gets damp it will also effect bad wires. my 2000 GTP was running like total crap. gas mileage was down to 17 mpg and power was way down. i replaced the plugs and wires because it was running much worse when it was snowing out. i also had a misfire P0302 code. i paid $32 for the plugs and wires and did it myself in an hour. i never personally did wires to the car so i had no idea how many miles were on them. they were actually A/C delco wires numbered for the cylinder so they might have been original, im not sure if delco replacement wires come with the cylinder # on them. one of the wires came apart in my hand, they were junk. i could have taken the plugs out checked them over, taken the wires out and checked resistance but im not going to put used stuff back on the car when the whole tune-up was $32. my gas milage also has gone up to 21+ MPG average huge difference that will pay itself off quickly.
those mechanics knew exactly what they were doing, throwing expensive parts that weren't needed bilking an older lady for expensive labor to fit it and saying "oh gosh gee, guess that wasn't it'. yeah okay, you might have thought it could have been an ISC problem or even something physically wrong with the throttle but unplugging the ISC to see if there was a behaviour change would have confirmed that there wasn't let alone the fact there wasn't a code or even doing basic multimeter tests or a physical inspection of the parts could have confirmed that they were fine. it shouldn't have cost anything other than an hour of labor (which they billed her for anyway for their misdiagnoses) and maybe a $3 gasket to eliminate those as possible causes to which you think "Okay so the engine has no problem with air intake, maybe its not the intake thats the problem" I mean DUH complete hacks
I have only watched two of your video’s - and I most definitely subscribed to your channel - You know EXACTLY how to properly troubleshoot and diagnose any engine malfunction and properly make repairs. Thank you so very much for sharing your knowledge - I am a mechanic also - BUT - indeed learn very much from your video’s. Keep up the good work - I would let you make any repairs on any of my vehicles - knowing that YOU know what you are doing and having FULL CONFIDENCE the job would be done correctly. You are VERY KNOWLEDGEABLE technician - certainly not a simple parts changer. GOD BLESS YOU 👍👍👍👍✌️✌️✌️
0:58 🤣🤣🤣 I agree. I would love for someone to explain who one would want a 4 cyl that sounds like a V8 and moves like a lawn mower. It’s embarrassing🤦🏾♂️
Just wanted to mention that with a clogged cat you will most likely have a large negative fuel trim (assuming the front oxygen sensor works). That is what I saw on my Dodge Ram Magnum 5.9, fuel trim was going to -30. That makes sense due to the engine not able to inhale as much air as the ecm expects, therefore the ecm starts trimming down the fuel to match the actual air intake.
Answer to a question I asked on Erico's channel this week. Even a semi clogged cat should show signs of negative fuel trims, as you stated, the air is restricted and the computer cuts the fuel to get stoichiometry.Very sound logical thinking. Must have a peek at the back pressure on my Toyota as negative fuel trims increasing over time.Notice too when I take out the air filter the trims decrease.
Good video Matt! I've had good success with the vacuum gauge in the past for exhaust restrictions. And as you've done, I do a follow-up with a pressure gauge in the O2 port to finally nail it. Nice work...
They make defouler pipes, to pull O2 sensors back and away and show a good catalytic converter when it's really bad. I don't advocate that kind of repair, but I think it'd be a good way to hook up the gags too. Unlike Matt, I don't happen to have a pipe that's just right. :)
Really enjoy the videos. Please continue as i find them a really good balance of logic, information and encouragement. I especially like the Beavis and Butthead reference in this one.
baz770 Lol, you do realize you you used "logic, information and encouragement" in the same parapgraph as "Beavis and Butthead" lol... that's priceless and actually represents my channel pretty well!!!
Just went through this hell with a 97 explorer. Did not want it to be clogged cats. Did everything else including fuel pump. Finally decided to use a digital meat thermometer. Touched the pipe before and after the cat. One side was about 200 degrees before cat the other side tested 450 degrees before cat! Didn't even need to test after cat! 450 degree at engine side of cat is a clogged cat. easy way to find clogged cat. wish I thought of it sooner. Will never forget. Cat should be about 100 degrees hotter on downstream than it is on engine side of cat. Kudos to my wife with the digital meat thermometer idea.
Usually by driving the car, you can feel the restriction . I diagnosed a few clogged cats simply by driving the car and listening to "bouncy" noises like that intake noisy, the whistling at the EGR due to backpressure building up. But yeah, getting a vacuum gauge to fit in there is 100% proof. There should be no "pressure" in the exhaust system, there should be more vacuum. Oh yeah, and on a car like that, it's going to have either 2 or 4 cats since it's a V6, a hefty repair. It's good to do both at the same time since the other ones are probably not any better.
just curious- how do you know when you have to diagnose vs just guess? For example how do you you know those symptoms were from clogged cat vs DBW system with a fault TPS which would cause same exact symptoms?
Also how are you seeing VACUUM in an exhaust system?? That is impossible, an exhaust system cannot possibly have vacuum. Where are you testing that would see vacuum?
Schrodingers Box I wrote " more vacuum " but i should have been more specific, since on your gauge it was showing 10psi and i ment that it should be a lot lower, but mis used my words. I usually have a car on the hoist and I can hit the cat with a light hammer and hear the material that has caused it to collapse shake. You also hear a different noise from the exhaust when you drive it, thus ruling out any " tps , or "maf" problems. When you see 10 cars a day you will learn a sense. Also chances are if you have tps or maf problems, you would notice them before hitting 2500 rpm or so unless they are very " specific " problems that " only " happen after that, because typically with a clogged cat, you will be stuck at a certain low to mid rpm , that will very slowly climb when you floor it. I guess its called experience
When I first clicked on this video I thought blocked cat (only because I have this problem before with the low revs) Iv also had this problem another time and it was throttle body but obviously showed up with scanner as throttle body codes , decent diagnostics I like the effort you put in to get right to the problem
the vacuum is supposed to drop when you increase the RPM. the max vacuum is in idle speed because the throttle body is allowing less air to get pass to the intake manfold. smaller gap = bigger vacuum. GREAT VIDEO!
Exactly correct- the more throttle the less vacuum- which makes reading the drop in vacuum a little tricky with a gauge- the lower vacuum you see with partial throttle should remain constant. If the exhaust is plugged, then it won't remain constant as backpressure builds up more and more. Actually Max vacuum on an engine is on a deceleration- on a properly breathing engine if you "blip" the throttle wide open and let it snap back, the vacuum will be high to start with (Idle), drop with the WOT, but then reach its highest point soon after letting it snap back closed (decel). and then return to the idle reading very quickly.
lol been chasing down little things wrong with my 89 mustang 5.0 and i am broke you vids has been helping me out alot and i find it funny that this is a 2001 sable.. i am using a tps from a 2001 sable, the air box, some temp sensors, grounds, head lights, and this has made my noght not only am i learning more about cars i now know alot of 2000 model sable parts will work for a foxbody
I wish you were located in Indiana. This sounds like my car. I have a 2008 Impala. I have replaced the wires and plugs, mass air flow sensor, throttle body, and pedal position sensor. All for it to be sitting in my back yard not able to go over 15 to 20 mph. I have come to find that shops around here even the dealers are shady and just want a quick dollar. Smh
Jayden Shoemaker Yep- all of those are pretty much what you would expect someone who doesn't diagnose a car to guess at. The car in this video had all of those and then some... An easier thing you might be able to arrange- just have someone (or yourself maybe) remove the front O2 sensors. While it will be loud as hell, if you remove the front O2s and the car goes much faster, that alone would be 99.99% confirmation you have a plugged cat
I love a vacuum gauge! They used to make one so you could do early "economaxing" for gas mileage while you were driving. I think GM even installed some from the factory on some mid70, early80's cars.
it should run hotter (motor and exhaust) if clogged. its nice to see an honest guy like you, with good info. p.s I have no auto problems I just happened to run across your video and enjoyed it.
Fantastic diagnostics with the evidence to prove it. I have run across this before and I usually pull the O2 and this is enough to bring the rpm's back up. Been a while, glad to see another great vid.
Thanks Steve- I had considered that idea but was afraid the small relief from removing the 02 would not be enough to make a significant change. It is good to know that can be used as a simple test. Thank you!
Schrodingers Box On that car no. 2 is much harder to pull. I'm glad you found the restriction without dropping the catalytic converters from the manifolds (they Y together all in one piece if someone else is wondering). That can be a lot of rusty work....of course, I believe you ended up doing that anyway. :)
I like your analysis skills LOTS of money could have been saved and I feel bad for the customer.i think after the second fall in diagnosis it's time to move on to another mechanic. As a shade tree mechanic my self I don't get arrogant ever. I have a similar issue and planning to use your method thanks
I am assuming this was a clogged cat? I had one clog on me and will not forget that experience because it left me stranded on the at midnight in january cold spell. The vacuum gauge is a good check. A seat of the pants feel would be going up an incline or if it is worse on a level road, you need to keep pushing down on the gas pedal more and more to keep the same speed. You could also get out and look at the cat after running a few min. like that and you would see it glowing red. I am glad you did mention just remove the o2 sensors and you will notice a drastic improvement right away. Lot of great interesting stuff in your videos-to much actually, it is 3 in the morning and I am still excited watching your videos, I need to get to sleep-lol.
Hey, EXCELLENT video. And I like your style. Say, I'm at my wit's end here. Got a 91 Buick Century, which will start and run for about 10 minutes and then die, and won't start again until it's been sitting for a long time. It's not overheating, fuel pressure is good, just changed the fuel filter, sparks/coils all good, tested ignition module -- also good, changed air filter, ran diagnostic (OBD 1 so not real sophisticated), and only code I get is 26 which is "quad driver module circuit," which I believe controls things like the fan/what have you. I thought for SURE it's _GOT_ to be the cat, but just tested exhaust pressure with an exhaust back pressure gauge, and the result was that it stayed just around zero psi at idle, and somewhere around 1 psi at high rpms (though the gauge arrow will jump up to around 7 if you gun it in short spurts). ANY THOUGHTS??? Possible suggestions? I'm not even sure what to try or look at at this point.
Schrodingers Box Here's the deal, my man. In the list of all possible OBD1 codes specific to my particular vehicle (2 digit codes from 13 to 66, which you can see here: www.troublecodes.net/GM/89-91_33N_mfi/ ) do not include anything about running rich or lean. So how could I possibly know what my fuel trims are? Is it even _possible_ on my model?? (
I am having a somewhat similar issue, but more difficulty diagnosing. I do have a graphic scan tool. I have a '00 GMC K3500 pickup with the 5.7 Vortec motor. I have one hallowed out catalytic converter and I plan on cutting the other one out in the near future (my state does not require emissions inspection). I had an exhaust leak from the exhaust "donut gaskets" on both manifold sides. I replaced both gaskets. About a week after the replacement, I got a code P0134 (low activity H1B1 02 Sensor). My truck has absolutely no power. It will go up to 65, but it takes forever to get there. On my scan tool, I noticed that the mv for bank 1 sensor 1 and bank 1 sensor 2 both fluctuate between very high numbers between 450 and 900mv. On bank 2, the sensor 1 number is always high while the sensor 2 number is always around 47 to 60mv . With my limited knowledge of exhaust systems I assumed the bank 2 sensor 2 was broken or the cat was clogged. Long story short, watching this video, I feel like maybe it really is just a bad o2 sensor that's causing my extreme power loss?
I don't know what data do you have that shows its "just a bad O2 sensor"? What are your fuel trims? What variables were introduced to validate O2 response? I would need to see some data.
@@SchrodingersBox I don't think I can share photos via youtube, however both long and short term fuel trims are 0 which I believe is perfect. I don't have an actual wideband so I cannot determine real time Air-Fuel Ratio. I did order a fuel pressure test kit, but I don't suspect fuel delivery is the issue. The engine has no misfires per the scan tool. The only suspicious data on the scan tool was the o2 sensor readings for bank 1. It's strange to me that this happens after I finally "fixed" my exhaust leaks. My presumptions are; now that I've finally fixed the leak, air has no way to travel but through the cat which may have been clogged all along, or that the o2 sensor wire may have melted? I will try to check for continuity on the o2 sensor on the truck, but I'm at a loss.
There is not- I didn't film the replacement of the catalytic converter since thats pretty basic bolt-on stuff. But the cat was melted into an almost solid brick
Yes it did. In fact, it ran so well after the repair that the next day the owner, not being used to the new power and responsiveness, lost control of the car during a snowstorm and totaled it lol. True story.
Good stuff! One possible reason you didn't see scan data that time,could be because the car wasn't up to operating temperature,and was still in 'open-loop' mode. Once the O2 sensors and coolant,etc. get up to temp,the ECU/PCM (whatever you want to call it) should kick-in,and take over..and you should start seeing data. Thought it was worth a mention..might help explain the 'missing' scan data? One test for plugged exhaust,is to pull the pre-cat O2 sensor(s) and see if it improves with them out. But then again,lots of hot exhaust gasses coming out of everywhere is a pretty good clue! :) I once ran across a plugged cat. on an '86 Firebird - A V8 shouldn't be that gutless!
Hi again Phatty, glad you seem to be enjoying the channel! This communication issue with the scantool is actually just the result of having a $400 scan tool instead of a $4000 or even $10k scantool. It occassionally just drops communication and you have to actually reboot the laptop to get it to work again and i just didnt have time to do that. Its frustrating and often happens when i am doing test drives and stuff. Oddly, using a screen capture program while running AutoEnginuity invariably causes the same issue so It makes recording data for later use in videos impossible. Someday.... a Verus.... someday!
I've been working on cars since the 1970's. Former Master ASE tech. You use logic and common sense in your diagnosis. What is wrong with you? Just kidding, I am thoroughly impressed with you.
i just found this was my problem with my blazer.... anyway i am 90% sure this is main issue... black plugs,no power,bogs down when i give it gas...I replaced everything else you mentioned... my fingers are crossed...to make sure i will test back pressure in morn... thax
Once I had a truck died situation. When I stopped for a red light and went to go, it died. Once I popped the hood and saw the exhaust manifold glowing bright orange I knew what had happened. However, I had no symptoms leading up to the failure. Once it was confirmed, the fix was easy. Blocked Catalytic converter.
Now, I am driving a 94 F150 5.0 AT as opposed to an 88 F250 5.7 5 Spd ( the truck that got blocked cat) Having worked my way through testing the various components , EGR, MAF, IAC, Throttle Position Sensor, etc and vacuum lines, I am mostly sure I am doing things right and believe thus far all is within spec. Yet, I still have a mostly smooth idle, but have gotten a harder to start and keep running scenario. The main symptoms that caused me to need to diagnose things is the more prevalent and more frequent loss of power and sputtering/bucking type behavior when I go to accelerate up a hill or get up to speed like getting on the highway etc. In addition, I get the loss of acceleration and the knocking sound of like when the timing is retarded too far when going up hills etc. But this clears up when trans is in neutral and at idle or even when given pedal. As it sits, I am attempting to rule out the simple causes like old, bad or loose plug wires, cats, etc. Thanks for your teachings and demos. I am doing my best with OBD1 limitations and my own learning curves.
Hello I'm five minutes into the video stopped looking diagnosed catalytic converter by what you said curious to finish watching video to see what you find thank you for your help .
Hi Matt Arr, well at least I'm thinking in the right way so I must be getting some of this. Thanks a lot and I really appreciate your time in educating us. Thanks a bunch.
i remember first entering the automotive world, wondering was i crazy that so many “master techs” had no clue what they were talking about “you need all 4 oxygen sensors” on my crown victoria lean codes on both banks, i remember thinking i was crazy, cleaned the maf, car ran like a champ. never questioned myself again
I did not see the vacuum gauge drop it looked steady to me while the engine was reving. Now maybe i am looking at the numbers backwards like the needle going up on the gauge is higher and down on the gauge is lower vacuum pressure. Anyways I just wanted to point that out. I like your common sense approach I think you are a good teacher and you are humble enough to not let your ego get in the way of your learning. You have great videos man good luck.
Great video on exhaust restriction. Again, your videos make more sense than others. There's always the teacher that matches better how a student thinks. I'm glad I found you and I'm glad you share videos. Don't feel bad about listening to the alternator. I laughed. My mom has those cars and she's about the same age as this car owner. Can I say that? lol. Anyway, it's a resonant point of sound, and even though I know it doesn't mean anything, I always have to look at it when looking under her hood playing, find that sound.
Been a mechanic for 38 years and I have never let a customer pay for my mistake. Put that kind of pressure on yourself and you will become a great troubleshooter in a very short time or you go out of business.
ive had recent dramatic success with cleaning out the CATS: I drilled a small hole in the exhaust just before the CAT and while the engine is warm and running, I spray bursts of CARB CLEANING via a straw into the hole. (I do both sides- since I have a GMC van w 2 cats...) The drivability change is very pronounced! I use an entire can. I used a can of intake cleaner also once - w PEA.
I don’t follow- how can drivability increase? Catalytic activity has nothing to do with drivability. What drivability improvement are you experiencing?
Do any cars monitor the pressure in the exhaust either directly or indirectly? Is there a trouble code for high exhaust pressure? What are typical codes that might get triggered when the exhaust is restricted?
The shop paying for things if they are wrong is exactly the kind of incentives structure needed for shops to not screw over customers or jerk them around, lying, dodging, coming up with new diagnoses, all at the customer's expense. The auto repair industry has an incentives problem. That's my diagnosis
This happened to my dad's 06 Altima V6 and it killed the engine. It took me 2 weeks to diagnose (Luckily I learned from you not to throw the parts at it until i'm sure :) The front pre-cat fell apart and clogged the exhaust completely. I guess under huge pressure some of those pieces were sucked in by the engine (too close to exhaust ports) and it killed cylinders #2 and #4. Compression on #2 was 75, #3 was 90 while the other 4 cylinders were all at 145/155 (dry/wet test). Believe it or not the car still pulled hard (AFTER we changed the cat) but smoked like a chimney. He had to add 1 quart of oil every other day. We had to replace the engine.
Mickey Bauer That's unfortunate but good calkl. Yes, running the car in this condition can be quite damaging. I actually had another one come in since this video- but by the time the person brough it in, the engine was making a terrible pinging sound and it turned out to have no compression in a cylinder clearly due to a broken valve.
![Lp. Сердце Вселенной #60 РОЖДЕНИЕ ЛОЛОЛОШКИ [Финал] • Майнкрафт](http://i.ytimg.com/vi/YoR0pAV9FVQ/mqdefault.jpg)
As a mechanic, ive sat in auto dealerships waiting to pick up a part at the parts dept and listened to the service desk presenting lists of "repairs" to poor unsuspecting souls..hearing the diagnosis and the parts and labor pricing is almost painful at times becuz i know what the real time involved for the work done should be and i know what the parts pricing should roughly be... its so sad... people are being fleeced alive, especially old people and women....these shops take full advantage of people ignorance and their helplessness to to their own repairs....integrity and ethics are often absent in this field.
it comes from being continuously in contact with humans that know ZERO about how cars work, the frequent " my car won't start , I think the starter is bad..." mechanic finds it was a burnt fuse, being honest will put maybe $ 20-30 bucks in his pocket, or letting the customer believe he was right, And charging him for the new starter,( which goes straight into his pocket cuz the old one works great and is already installed) ,and the imaginary 3 hours of shop rate in labor to install the imaginary starter, the customer's happy to pay it, and $30 for honesty , vs. $400 -600 for nothing........ they get used to easy money, and in time burn anyone and everyone... I think all mechanics should have three random repairs every 5 years, that are actually employees of the BAR, who bring in cars with issues , pre determined, and report on the mechanics, ability, how he went about diagnosing cause of issue, did more charges than needed appear on the bill, did any of the loose 1 & 5 dollar bills stuffed in the cupholder disappear, or the gold chain half hidden by drivers floor mat?
I just got ripped off by a mechanic who quoted 3 estimates...$500 to get it to run better, $800 to be able to get on the freeway, and $1200 for everything to work right...one mechanic didn't clue in his partner what I was quoted, and when I brought the car in the next day ( having no other option)only the partner was there, I had to ask him , if there wasn't usually something I signed , that had a price and what needed to be repaired? He then asked me what the other guy quoted me....& hastily wrote $500 when he saw the look on my face....I came back to my car having the same exact issues, returning to them, then he told me the ECU needed to be replaced...and he had already ordered it, but wouldn't arrive for 2 days....so I went and got the exact same ECU and brought it to him ,but he now couldn't program it , and sente to his locksmith buddy who did it in 5 minutes, and charged me $300....I did a throte relearn, and the car ran exactly the same...same issues, no change... $500 for vague wiring repairs $65 for diagnostic/engine trouble code printout, which told him the same that I did when I brought the car, $140 for tested used ECU, and $300 to program it......$1000 later, and I'm the same exact place I was before...
I'm going to his shop tomorrow, and I'm so pissed off, I can barely see straight...my Nissan buddy finally gets back to me, so I ask him why would mechanic tell me he found the problem, make the repair, release the car to me only after payment, the problem not be fixed and then state he found the real cause of the problem... "To take your money" , my buddy says......
what do I do next?
Does California Automotive Repair Act , permit a customer blatantly ripped off, to pummel the crooked mechanic until he agrees to fix it right, and right now?
I absolutely love your shop policy, more shops need to implement this policy: If you are unable to fix the problem, the parts come out of your pocket. There are too many mechanics out there who just throw parts at a car and pray that it fixes the problem. Good to see techs out there who value the customer's time and money.
I cannot remember how many times I have paid for parts that were not broken. Sir you are a breath of fresh air. Finally I find a mechanic who does not shotgun a problem with parts until the problem goes away.
Many thanks my friend. Indeed buying parts should be the result of the diagnosis, not the method of it. But it takes knowledge of systems to do the diagnosis and I appreciate the few people like you who are willing to dedicate time and effort to that. In fact it is exactly why I made this channel.
BChrisQq
"If it breaks it needed replacing anyway" ~ Murphy's Law, 1982
02 525 i will not exceed 1000 rpm
@@bridgotslattery4667 you should try it.im sure you'd enjoy it.
And the award for world's best mechanic and most stand up person goes to: this guy.
Also I really appreciate the fact that you were going to buy the part for her if you were wrong about it
I agree, I am just a backwater mechanic, but I find so many people don't have the slightest clue, even the one's that do this for a living. You have the skill, just figure out what's not causing it, and test to see what it is. I laughed at the frozen piston part. Good job, we need more like you that know how to look outside the box.
@Matt, all of those issues I have been having with my 01 S-10 4.3L were because of a clogged pre-cat, and it blew out the back half of it into the primary cat. Recently, the vehicle would hardly get out of its own way, and on the road it wouldn't accelerate for $hit!! Other than the obvious symptoms, I used an infrared temp gun, and the temp at the back of the pre-cat was 150* lower. The engine was bucking, fuel trims were very lean, was throwing a P0101 code, P0300/P0304 code(s), burning excessive fuel, etc. Also the post cat O2 was almost pegged out at 0.85 volts constantly. Took it to an exhaust shop where they did the same back pressure test, and at 2500 RPMs, it was almost 6 psi. They replaced both the pre and main cat with just one cat, and now the truck runs great!! Several misfiring incidents over the past several years (corrected now) led to the cats being destroyed. Hope this is helpful info to anyone that watches (and should be!!) watching your channel.
This guy is better than at least 90% of the accredited mechanics working at shops
lol bunghole sadly only teens who survived the 90s will understand
shattered79 Beavis and Butthead. “I am The Great Bungholio!
There are no more teens from the 90s.
@@e.v.a.l.s 🙋♂️
Hehhhhhhh i need t-p for my bunghole hehh
"survived" the 90s is correct sir. We all had it so good but we didnt appreciate it enough. lol 90s were the shit
This channel is addictive 😅 one day a fuel trim video popped up and ever since is a non stopping thing I watch at work, during lunch and even before going to sleep.
Hahaha yeah I often find new viewers “binge watch” upon finding the channel. Hundreds of video so good luck sleeping lol!!
Hi, I would consider it pretty normal that the vacuum gauge reads 0 when you try to rev it with a clogged exhaust. In normal operation, intake vacuum is maintained by air flowing in being restricted by the throttle valve. If the restriction is elsewhere, the pressure difference will be elsewhere too.
In this case the idle vacuum was already extremely low, which indicates a problem right away.
Vacuum gauge can also be helpful in diagnosing a burnt intake valve. Average vacuum will be almost normal, but the gauge will flutter synchronously with the engine speed once per 2 revolutions.
In fact I consider the vacuum meter as a very useful tool, but as with all tools it takes some explanation and practice to be used effectively.
i like a vacume gadge+ i hooked one up on my car.
I wish there were mechanics like you around everywhere !! All there want is money now and don't care ! :(
Yeah, your right how dare people make money from your ignorance of mechanical knowledge. They should just have a free service for people who need love and their car fixed... all free, yeah that's how it should be.
findvoltage well there is actually ignorant mechanics that try to solve problems with improper diagnostics, and that’s when they “want money”. She’s obviously not talking about all mechanics, which is why he said WE WANT MECHANICS LIKE HIM. you’re a dumb ass 😂
findvoltage I mind when mechanics make money from their mechanical ignorance...don’t mind one bit if they make money from my ignorance! To boot they’ll fuck up something else _as in this video_ Ill recommend watching it 🤪
Agree😔.
This was a BIG win for you! I'm grateful that i can learn from you.
What a stand up guy! God bless you sir!!
exactly!
"Actions speak louder than words!"
Too many people that dress like and try to sound like Pros dont come up to your ankle 🤗
After replacing melted catalytic converter the key to ensure the replacement won't melt in short order... I guess "old lady" drove ignoring CEL caused by old plugs.
absolutely! how many mechanics do u know who would stand behind their work like that?
As a training tech in a dealership - thank you for the theory! Throwing darts isn't fair for anyone.
It's sad that there are people who say they are "certified" and can't even diagnose a problem. This is exactly why i'd prefer to do the work/diagnoses my self with the help of youtube of course. keep on keepin' on. Your video's are great btw, and have helped me a great deal. thanx
I know this is an older video but I am constantly amazed at how very few people see the value of a vacuum gauge as a diagnostic tool.
I have just diagnosed the very same issue on a Mazda Tribute v6, like most others, the first thing I turned to was the scan tool expecting to see everything pointing to lack of fuel.
Surprisingly, upstream O2 sensor was cycling and fuel trims were within the realms of normal.
Next hook up for me was a vacuum gauge as I was already suspecting an exhaust restriction. I got exactly the same response as you did, lower than normal vacuum at idle and very low, near zero at revs. I have seen this many times before in my 40 plus years in the trade, it pretty much confirms a blocked exhaust.
I am in an industrial area so I dropped the exhaust, first after the cat, no difference, then before the cat and the vehicle was able to rev freely.
First problem solved, now to find out what caused it. :-)
In this application, the gauge was able to give some unscientific indication to support a restriction hypothesis, but it was the backpressure test using the vacuum gauge, not the vacuum test, which ultimately gave the scientific validation.
Seeing as how lower vacuum occurs at open throttle, it should be apparent the scientific application of a vacuum gauge is invalidated for this test due to lack of an independent variable.
As you also indicated the fuel trims in modern vehicles also completely invalidate ANY application of a vacuum guage in modern engines.
For the vast majority of diagnostics in OBD2, a vacuum gauge is useless in scientific methodology. In fact I even having a video showing how the PCM's stoichiometric adjustment even fools the gauge into indicating there is no problem despite an obvious issue being present.
I can tell your a good mechanic because your not afraid to say 'I'm not sure' or read some directions off a rarely used tool.
The ones who know everything and are always right waste so much time and often other people's money trying to prove it so.
And your rational mind lends itself to problem solving.
Funny as soon as you talked about the systems of this car, I said it had an exhaust restriction. I am a very old mechanic and back in the early 70's GM had a very bad exhaust problem. They had a double walled exhaust pipe before the muffler for those who don't know where the exhaust pipe is. Anyway when the car got hot and it was raining and you went through a puddle and hit water onto this pipe it collapsed but only on the inside. If you looked at the pipe it looked fine from the outside but the car didn't go over 25 MPH. After the first 2 I diagnosed the problems in less than 1 minute. No power, hissing noise under the car either moving or not, just trying to rev the engine. Now the vacuum gage is another tell of this problem and will accurately diagnose this problem every time. But after cats came out I found both a clogged cat and a broken apart cat with the insides stuck in the muffler clogging the exhaust. But you are right after you fix this problem you need to find out what caused the cat to go bad.
I was quite surprised to see that the vacuum gauge worked to identify the backpressure on a PCM equipped car. In the days prior to PCMs, I used a vacuum gauge quite often to diagnose engines. Before the days of scan tools, it was an excellent means of diagnosing ignition timing problems, fuel mixture issues, vacuum leaks, sticking valves, and exhaust back pressure.
However, in cars with a PCM, the PCM can make changes much faster that the vacuum gauge can read, and have mostly rendered the vacuum gauge useless. My old vacuum gauge sits in a tool box with my dwell meter. Museum pieces.
I am a Trans Am guy like you, and my one experience with a clogged exhaust happened on my 1976 Trans Am in the early 80s. I was driving home from Florida to North Carolina when the car lost power. I couldn't go faster than 40 mph and the engine overheated at any speed over 30 mph.
On the side of the road I used my vacuum gauge and got the same results you got, indicating a clogged exhaust system. The 76 Trans Am had a different kind of catalytic convertor than the modern ones in that it was filled with catalytic beads. There was a screw on cap on the bottom of the catalytic convertor that I could remove with an Allen wrench to cleared the beads out of the convertor. Fortunately I got enough beads out of the convertor so that I could make a normal drive the rest of the way home where I installed a bypass pipe in the place of the convertor. In the 80s leaded gas was cheaper and more available then unleaded, so I would run leaded gas in the car. I believe the leaded gas had fused the beads together, which created the blockage.
One last question Matt, could you have seen the clog reading the intake manifold pressure and the barometric pressure on the scan tool?
Totally agree with you. One way you can tell a "mechanic" doesn't know what they are doing is they use a vacuum gauge on a modern car. Actually to be honest, most people who used them on older cars stuill just guessed anyway because the results are subjective.
The exception however is with what I did in this video and using the PRESSURE gauge on the exhaust. Regardless of the car's design- a clogged exhaust WILL increase backpressure and the car cannot make adjustment for it. You WILL see backpressure. So in this case the vacuum gauge is reliable. ALso- yes, absolutely (no pun intended) you could also use MAP and see there is excessive pressure in the intake manifold.
You can also see it through the DPFE on Ford vehicles as well.
Great comment and question.
Excellent Video ... love to see someone who knows what they're doing.
Brilliant ... learned a lot.
Many thanks .
Dude , I can't thank you enough for sharing your knowledge on diagnostics. I'm subbed to your channel and can't stop watching. I'm not a professional mechanic, but lovee to turn wrenches on my own stuff along with family. You have helped give me arsenal of weapons for diagnostics. Actually chasing a very similar issue. Had thought it was vacuum, or 02. Changed the O2 's because the car sat for years and noticed some material on the b2s2. Any how , I'm off to a vacuum test!!! Thank you for saving my money !!!!!!
What I really like about you Matt, that you don't stop at changing the faulty part (in this case the clogged cat converter), but you wanna find out what caused that issue at the first place. Even if the customer doesn't want to fix the main problem yet. At least now s/he knows about it. I've never seen a mechanic like that. Absolutely AWESOME you are!!!
Wow thanks man. Yes- understanding the cause is the most important part of confirming a permanent repair!
With all of the replacement parts, this car must have been humming afterwards. Hope the lady took this into consideration! Comprehensive video.
The vacuum gauge has turned into a tool of the past. Good to see it used here. The vacuum gauge was very useful to me as a young mechanic working in a high volume trans shop for 5 years just out of high school in the early 80's. Back then on GM and Ford, no vacuum= very late or no upshift at all out of first. Back then, engine vacuum was like a "load sensor" for the trans, along with the kick down cable or lever. I recently used my gauge as a quick way to verify good engine vacuum at idle after replacing upper intake gaskets on my 96 Ford explorer. On the car in the video, I would bet that your vacuum is higher at idle after the repair. 10 inches is too low at idle on any car. If you are not higher than about 17 at idle you know something is wrong.
AGreed!
I just got one with a plugged exhaust. But the service writer said to put coils and plugs in the misfire history cylinders. Its not always the mechanic but most of the time it is. The trick now is to figure how to determine exactly which one and how many. It has three. Thanks for the tip about the clogged muffler. Keep up the good work. people need to see honest techs with some good knowledge. My back pressure test blew my hose of my gauge,lol
"I need a gauge for my bunghole." had to replay it a couple of times, great stuff. Loving the videos! 😎
WOW!!!! I am having a similar problem with my 95 suburban, I am no mechanic but I have been fixing my own vehicles for 40 plus years. I also noticed the "sound" when I accelerated. Everyone I asked never noticed any peculiar sound! A couple of these people were mechanics. Up until I watched your video I thought I was over analyzing the situation, as is often the case with me. (I'm an Aquarius with ADD and OCD. Yeah) So thank you for the video it was well done and very informative!!
Who knew Beavis was a great mechanic! Good job
You are now officially my teacher all i don't know from now on I will be learning from you
I’ve been struggling trying to diagnose this problem with a Mazda 6 v6, bro you earned my respect! You are awesome
One of the best mec and well explained videos ever seen on UA-cam this guy is super smart and have plenty of knowledge on fixing and finding car mec issues
This old video is great. One thing I learned is clogged cats get really hot. You can diagnose a clogged cat with an infrared temperature laser, ingress and egress pipes, or benchmark in your journal what a normal temp cat would be at, and then take a temperature reading. other videos describe this. Also the exhaust coming out of the pipe will be super hot.
Thanks for posting this great video.I do work as a certified mechanic on daily basis,but i must say that i am impressed and grateful for these videos...it shows that everyday you got too learn something New..or at least update yourself.....To understand how it Works and too be interested in solving the problem.One of the better videos i have seen on you tube that involves diagnostic on cars and a better understanding on how too think.....before you change a part on a vehicle..Thanks again for making the car World a better Place.
Greetings Fredd from Norway
You are a Jedi Mechanic! May I be your padiwan.... honestly you make understanding mechanics incredibly easy. I learn so much every video I watch. Thank you
Good thing that the poor lady found you! I agree with ur diagnosis bro, its amazing all the "pros" didnt catch it! It was pretty obvious and well verified by ur tests.. one thing though, yes it may be the catalytic, but swapping a new one in there may yeild a temporary fix, as cats go bad for a reason! and the Cause of the original getting plugged up needs to be addressed or the new one will end up the same way down the line...Ive had new magnaflow cat melt the honeycomb and seen it crumbled inside after 6 months of use... im sure you already are checking into the cause... great vid
I take it you didn't watch till the end
Hi , I am from south Africa you are a life saver you save me thousands, thanks for the advice , you the man
Same here South Africa 🇿🇦 Mpumalanga. He is a life saver for sure. .
No mechanics like this where I'm at.
I currently have a vw cc acting the same way and fortunately caught the guy who put an secondary air pump on it was just going to parts change all over that engine before he ever got to the problem. Sadly I think he knew what it was but hey its 2020 and this year has truly changed people for the worse. I did yank the car from him but not before he removed a perfectly good part and replaced it with a $505.00 part. He literally told me he needed to replace every link in the chain of parts he believed was causing the problem. Told him no and took my car back home. Now it has been diagnosed with a back pressure exhaust issue in addition to a 1 plug and 1 coil replacement. $1958.00 estimate.
I have done my own research and was able to find all the parts for 600.00 and will be doing it myself.
An almost unbelievable diagnostic(?)approach history in this poor woman's quest to have her car operate normal.
I have witnessed over the years several other technicians with the same modus operandi to make maximum financial gain by using the very least amount of time and effort. The sad part is that they released the car back to her in the same or even worse condition that it was presented to them in the first place.Thank God she was led to you Matt.
+John Kimmel I see it allllll the time, unfortunately. All the time.
In fact, it got to be so friggin frustrating I decided to make a UA-cam channel a couple years ago to fight against this and empower the DIY to be more defensive.
I check my PM's and you never left your number. If you PM me with YOUR number I'll be happy to call. I leave town again on Sunday afternoon so if I don't get in contact before then I won't be able to help.
You, my friend, are amazing
I am hooked on your videos
I have an RV with a ford engine.giving me the lean codes that you talk about
Been to FOUR mechanics. Yes, parts replaced but error codes still come on. After there cleared, they come on usually a after fifty miles of driving
After watching your videos, I am going to try troubleshooting myself
Thanks for your excellent videos
Thank You! Eric the Car Guy also showed this vac gauge test for exhaust restriction detection.
Just found this - nice to find another mechanic who gets the left-overs after every other 'expert' has had a go!
I'm sure I'd be changing parts parts I wouldn't have to without this guy.
Really appreciated your intelligence approach . After watching your video my mind is turned back to my Toyota Yaris 1.0L 2000 model old car probably old issue lack ok power forces to paddle reach to 100+ km/h buzzing sound while accelerating fast, LTFT +1.5 at idle , check exhaust seal was ok no cat converter in model , decided to check engine compression and found 3 of spark plugs found oil deposits coil plugged side , that’s was the issue leaks spark plugs seals , got a serviced well tighten well, wow amazing improvement LTFT exact on 0 in idle , it’s all created to you sir the core knowledge way you teaching ❤
I have had this p0420 code on my 2.4L '09 Camry for 3 to 4 months now. MPG and performance has been optimal the entire time. Oxygen sensors are new, exhaust is new, maf new, air, injectors...but not the cat. Everything passed the health check on the Techstream diagnostic report except the catalytic converter p420....
I tried 'cataclean' and high-rev driving 4000-5000 rpm for about 50 miles a week ago (heard this helps clean the cat, makes sense) and this all improved the engine performance, but did not clear the code. I drove the car home from work yesterday (performance was still flawless even at high (5000-6000) revs, inclines, shifting etc).
The next time I drove it was today. it was pouring rain and had been pouring rain all night (maybe, maybe not relevant). After letting it warm up in the rain 5-min I engaged the gas and immediately there is harsh shaking, blinking cel for p0420 and p302 misfire I've never experienced. I thought perhaps something electronic got wet from rain? But, even after I did a soft-reset of ECU the symptoms, shaking, and blinking CEL p0420 returned... there was also a strange smell (not quite rotten eggs, but definitely unpleasant).
I examined the exhaust leaving tailpipe. There were half-second bursts of pressure & then no pressure which seemed in sync with the shakes of the car. Not even a mile from home, decided to take the spare Yaris to work; didn't want to cause more damage...
Do you think it is most likely the catalytic converter? Is it often for a cat to go that bad that fast? From no drivability/performance effects to completely catastrophic overnight? I thought a dying cat was supposed to be a gradual worsening...?
[Remiss of me not to mention the engine has 360,000 miles w/ original cat and transmission, but I have no problem replacing the cat myself with $250 one off amazon. I knew the day would come; just thought I'd see it coming over a longer period of time.]
No idea. what data do you have?
Thank you! You covered all the possible symptoms for restricted air flow. I am almost sure now the cat is the culprit to my problem. This was very helpful and I just subscribed. I'm now apart of the 2 percenters club.
We have a 2012 Mazda 6 in the shop now. No codes. occasionally throws a 0420 code with a note about warmup. the hissing kind of sucking kind of vaccum cleaner with out the motor sound is remarkable. Later today I will wander under it to see where exactly the restriction is. On newer cars that use a 14mm fitting for the 02 sensor you can you a Dorman Spark plug non fouler to create your "bung hole" fitting. Great video. Nice to see good guys (and little old ladies) winning one.
Good job SC. Hear is one for you. I had a 2008 F150 with a 5.4l V8. vehicle showed multiple miss fires and my friend attempted to fix with just adding 1 coil. He immediately gave up and brought to me because he did not want to mess with the plugs if you know what I mean. How ever I verified the miss fires and replaced all over plug coils and plugs after finding more than 3 faulty coils and plugs with almost no electrode. Past experience shows that when one or more go bad the rest are not far behind. Anyway after repair the truck ran rough, had no power and bogged down however you could slowly get it to gain speed if you where feather light on the pedal. I immediately knew it was a restricted exhaust. This truck has 2 cats one for each bank. Now I did test vacuum and my reading was normal 22-25 in/mhg and steady so you would think it should be low. Tested pressure before cats, pass side 2 psi at idle, 5 psi @ 2500 RPM as manufacture test procedures, driver side needle would just bounce from 4 to 10 psi and peg at 10 at 2500 RPM. Ford test specs for this truck or engine are 4 psi at 2500 RPM as ok. I also put a scanner on this truck and monitored live stream and O2 sensors normal and changing lean-rich as normal with short & long fuel trim with in range. I just wanted to Pass on that in your video you stated that anything over 2 psi is a restriction I just think that you should have them refer to manufactures testing data results instead because, 2 psi might fit a good number of vehicles just not all. My friend told he drove the truck before any repairs on a trip for a long distance and it ran with missing and pinging and lost power over weeks.
Thank you very much for sharing.
07 f150 5.4 Triton,40k mi., 8 miles to the gallon, low power, smells like sulfur, , makes a waaa noise when accelerating, no codes, mechanic put it on some sort of cheap scan tool no problems found
Should I go somewhere with a more sophisticated scan tool for Fords ?does anybody know what these more sophisticated scan machines are called for Fords?
Maybe I should get the cats checked, Ford technician said to check for falling/failing BARO pid.
Any tips of the day from anybody would be appreciated
+steven lesher Drop cats at manifold and drive to see if power gains come back sounds and smells like bad cats. now when you do this if you have not already the cats wont drop all the way down but will work. if you use a pressure gauge in place of dropping cats ford says max 4-6 psi but you should see almost none. Cause is usually cylinder misfires on one side usually the affected side. the codes wont set a hard code until the problem occurs for a specific amount of time which will turn on the check engine light. however it will reset if the problem goes away for so many key starts. hope that helps if you have not already fixed.
***** You certainly broadened my knowledge friend. That's why I'm in these discussions.
+DE Nichols thank you for the reply. I can give you a little bit of other knowledge on the checking back pressure on the exhaust if you care to know. You can use a dedicated exhaust back pressure gauge but if money limited you can use a vac/pressure gauge. Just make sure the hose is long enough to reach into your hand while sitting in the vehicle and for reasons is so you can see the gauge while you test and for the most important so you do not burn the gauge with super heated exhaust gases and burning your hand, however you cant test for like an 1/2 hour the hot gases will surely heat the gauge and burn your hand do to conduction and radiant heat. I found an brass adapter with a barbed end at the auto store or homedepot / lowes to match the threads of the O2 sensor and used a fuel line with clamp reduced the hose down with smaller diamiter hose to fit vac/pressure gauge hose. just remember you only need a few minutes if that to see if pressure rises at idle and at high RPM.
You can also check engine vac with the same gauge to anchor your diagnosis as a double verification.
Well I'll be dammed.... I think I finally found a person that would make me feel like im working with myself... ladies and gentlemen I am far too humbled to be saying this with pride or self centeredness... I'm just speaking my truth. I have felt like there was something very wrong with my style of work. I've been told that I'm a technical freak and a complete overkill. I've been told that I'm a bad mechanic because I act like an "elitist". But I keep to myself verbally and I just do my work....I dont make others feel badly and certainly don't try to make others LOOK badly. God works in funny ways to have my stumble across this video when I wasthinking of abandoning my trade. But this is really how my call to action was meant to be. The best I can be. Thanks for sharing your skills and knowledge of a higher order
Hi. I have Datsun Go, 1200 cc petrol engine. My car recently involved in a car accident. It crash the back of an old car which happen to have stronger body tham my car. So the front of my car is wrecked. I have fixed it. But after 100 km the car loses its power. Seems like the throttle can not reach its maximum power. It stopped at half of the digital indicator. What do you think probably cause it? I ask local repair shop (not doing any test yet) they say "the throttle sensor" cause it. I have spent a lot of money to fix the car after the crash. Please help me to decide what to do next. I dont have much money left :(
Start with seeing if your signal outputs are proportionate to the variable resistance of the potentiometric position on the TPS.
Schrodingers Box I am not sure what it means. Because the difference of our language. But I will translate it and give you the update. Thank you for give your time to answer my question. Thats mean a lot.
sometimes ignition wires do fix the problem. usually that would cause i misfire and the car will run much worse when you put the engine under a load, and when the weather gets damp it will also effect bad wires. my 2000 GTP was running like total crap. gas mileage was down to 17 mpg and power was way down. i replaced the plugs and wires because it was running much worse when it was snowing out. i also had a misfire P0302 code. i paid $32 for the plugs and wires and did it myself in an hour. i never personally did wires to the car so i had no idea how many miles were on them. they were actually A/C delco wires numbered for the cylinder so they might have been original, im not sure if delco replacement wires come with the cylinder # on them. one of the wires came apart in my hand, they were junk. i could have taken the plugs out checked them over, taken the wires out and checked resistance but im not going to put used stuff back on the car when the whole tune-up was $32. my gas milage also has gone up to 21+ MPG average huge difference that will pay itself off quickly.
those mechanics knew exactly what they were doing, throwing expensive parts that weren't needed bilking an older lady for expensive labor to fit it and saying "oh gosh gee, guess that wasn't it'.
yeah okay, you might have thought it could have been an ISC problem or even something physically wrong with the throttle but unplugging the ISC to see if there was a behaviour change would have confirmed that there wasn't let alone the fact there wasn't a code or even doing basic multimeter tests or a physical inspection of the parts could have confirmed that they were fine.
it shouldn't have cost anything other than an hour of labor (which they billed her for anyway for their misdiagnoses) and maybe a $3 gasket to eliminate those as possible causes to which you think
"Okay so the engine has no problem with air intake, maybe its not the intake thats the problem"
I mean DUH
complete hacks
This channel is Amazing challenge for "pro " mechanics
Glad you think so!
I have only watched two of your video’s - and I most definitely subscribed to your channel - You know EXACTLY how to properly troubleshoot and diagnose any engine malfunction and properly make repairs. Thank you so very much for sharing your knowledge - I am a mechanic also - BUT - indeed learn very much from your video’s. Keep up the good work - I would let you make any repairs on any of my vehicles - knowing that YOU know what you are doing and having FULL CONFIDENCE the job would be done correctly. You are VERY KNOWLEDGEABLE technician - certainly not a simple parts changer. GOD BLESS YOU 👍👍👍👍✌️✌️✌️
Thanks man!! You made my day!!!
0:58 🤣🤣🤣 I agree. I would love for someone to explain who one would want a 4 cyl that sounds like a V8 and moves like a lawn mower. It’s embarrassing🤦🏾♂️
Just wanted to mention that with a clogged cat you will most likely have a large negative fuel trim (assuming the front oxygen sensor works). That is what I saw on my Dodge Ram Magnum 5.9, fuel trim was going to -30.
That makes sense due to the engine not able to inhale as much air as the ecm expects, therefore the ecm starts trimming down the fuel to match the actual air intake.
Answer to a question I asked on Erico's channel this week. Even a semi clogged cat should show signs of negative fuel trims, as you stated, the air is restricted and the computer cuts the fuel to get stoichiometry.Very sound logical thinking. Must have a peek at the back pressure on my Toyota as negative fuel trims increasing over time.Notice too when I take out the air filter the trims decrease.
Good video Matt! I've had good success with the vacuum gauge in the past for exhaust restrictions. And as you've done, I do a follow-up with a pressure gauge in the O2 port to finally nail it. Nice work...
They make defouler pipes, to pull O2 sensors back and away and show a good catalytic converter when it's really bad. I don't advocate that kind of repair, but I think it'd be a good way to hook up the gags too.
Unlike Matt, I don't happen to have a pipe that's just right. :)
Really enjoy the videos. Please continue as i find them a really good balance of logic, information and encouragement. I especially like the Beavis and Butthead reference in this one.
baz770 Lol, you do realize you you used "logic, information and encouragement" in the same parapgraph as "Beavis and Butthead" lol... that's priceless and actually represents my channel pretty well!!!
Just went through this hell with a 97 explorer. Did not want it to be clogged cats. Did everything else including fuel pump. Finally decided to use a digital meat thermometer. Touched the pipe before and after the cat. One side was about 200 degrees before cat the other side tested 450 degrees before cat! Didn't even need to test after cat! 450 degree at engine side of cat is a clogged cat. easy way to find clogged cat. wish I thought of it sooner. Will never forget. Cat should be about 100 degrees hotter on downstream than it is on engine side of cat. Kudos to my wife with the digital meat thermometer idea.
very good video matt, keep up the good work, hopefully the part changers mechanics learn something, thank you ,from ontario ca
Usually by driving the car, you can feel the restriction . I diagnosed a few clogged cats simply by driving the car and listening to "bouncy" noises like that intake noisy, the whistling at the EGR due to backpressure building up. But yeah, getting a vacuum gauge to fit in there is 100% proof. There should be no "pressure" in the exhaust system, there should be more vacuum. Oh yeah, and on a car like that, it's going to have either 2 or 4 cats since it's a V6, a hefty repair. It's good to do both at the same time since the other ones are probably not any better.
you didn't diagnose the car then. you used symptoms to come to an inference. There is a huge difference.
Schrodingers Box thats fine, i diagnose a car when necessary, thank you :)
just curious- how do you know when you have to diagnose vs just guess? For example how do you you know those symptoms were from clogged cat vs DBW system with a fault TPS which would cause same exact symptoms?
Also how are you seeing VACUUM in an exhaust system?? That is impossible, an exhaust system cannot possibly have vacuum. Where are you testing that would see vacuum?
Schrodingers Box I wrote " more vacuum " but i should have been more specific, since on your gauge it was showing 10psi and i ment that it should be a lot lower, but mis used my words. I usually have a car on the hoist and I can hit the cat with a light hammer and hear the material that has caused it to collapse shake. You also hear a different noise from the exhaust when you drive it, thus ruling out any " tps , or "maf" problems. When you see 10 cars a day you will learn a sense. Also chances are if you have tps or maf problems, you would notice them before hitting 2500 rpm or so unless they are very " specific " problems that " only " happen after that, because typically with a clogged cat, you will be stuck at a certain low to mid rpm , that will very slowly climb when you floor it. I guess its called experience
When I first clicked on this video I thought blocked cat (only because I have this problem before with the low revs) Iv also had this problem another time and it was throttle body but obviously showed up with scanner as throttle body codes , decent diagnostics I like the effort you put in to get right to the problem
The best explanation video on exhaust restriction
the vacuum is supposed to drop when you increase the RPM. the max vacuum is in idle speed because the throttle body is allowing less air to get pass to the intake manfold. smaller gap = bigger vacuum.
GREAT VIDEO!
Exactly correct- the more throttle the less vacuum- which makes reading the drop in vacuum a little tricky with a gauge- the lower vacuum you see with partial throttle should remain constant. If the exhaust is plugged, then it won't remain constant as backpressure builds up more and more.
Actually Max vacuum on an engine is on a deceleration- on a properly breathing engine if you "blip" the throttle wide open and let it snap back, the vacuum will be high to start with (Idle), drop with the WOT, but then reach its highest point soon after letting it snap back closed (decel). and then return to the idle reading very quickly.
lol been chasing down little things wrong with my 89 mustang 5.0 and i am broke you vids has been helping me out alot and i find it funny that this is a 2001 sable.. i am using a tps from a 2001 sable, the air box, some temp sensors, grounds, head lights, and this has made my noght not only am i learning more about cars i now know alot of 2000 model sable parts will work for a foxbody
I wish you were located in Indiana. This sounds like my car. I have a 2008 Impala. I have replaced the wires and plugs, mass air flow sensor, throttle body, and pedal position sensor. All for it to be sitting in my back yard not able to go over 15 to 20 mph. I have come to find that shops around here even the dealers are shady and just want a quick dollar. Smh
Jayden Shoemaker Yep- all of those are pretty much what you would expect someone who doesn't diagnose a car to guess at. The car in this video had all of those and then some...
An easier thing you might be able to arrange- just have someone (or yourself maybe) remove the front O2 sensors. While it will be loud as hell, if you remove the front O2s and the car goes much faster, that alone would be 99.99% confirmation you have a plugged cat
Thank you so much. Any advice helps at this point
cat converter
Jayden Shoemaker you fix the car yet
Jayden you ever got you car fix ??
I love a vacuum gauge! They used to make one so you could do early "economaxing" for gas mileage while you were driving. I think GM even installed some from the factory on some mid70, early80's cars.
Haha yes, I recall the gm’s with the “fuel economy guage”
it should run hotter (motor and exhaust) if clogged. its nice to see an honest guy like you, with good info. p.s I have no auto problems I just happened to run across your video and enjoyed it.
+mrcoltar15 unless its overheating the engine is that a really bad thing?
You are a master... ONE of the best mechanil that help other people....😂
Fantastic diagnostics with the evidence to prove it. I have run across this before and I usually pull the O2 and this is enough to bring the rpm's back up. Been a while, glad to see another great vid.
Thanks Steve- I had considered that idea but was afraid the small relief from removing the 02 would not be enough to make a significant change. It is good to know that can be used as a simple test. Thank you!
Schrodingers Box On that car no. 2 is much harder to pull. I'm glad you found the restriction without dropping the catalytic converters from the manifolds (they Y together all in one piece if someone else is wondering). That can be a lot of rusty work....of course, I believe you ended up doing that anyway. :)
DE Nichols When I replaced it, it was for the pipes around the catalytic converter leaking rather than a restriction.
I like your analysis skills LOTS of money could have been saved and I feel bad for the customer.i think after the second fall in diagnosis it's time to move on to another mechanic. As a shade tree mechanic my self I don't get arrogant ever.
I have a similar issue and planning to use your method thanks
brilliant diagnosis this was a big help to me all i do on my car is spark plugs lead and router...now i know it should be the exhaust..... thanks BRO
awesome diagnostics video on exhaust restriction.Being a young mechanic I learned plenty in 20mins#thankyou
I really like the way you wrench.Awsome video man ty
I am assuming this was a clogged cat? I had one clog on me and will not forget that experience because it left me stranded on the at midnight in january cold spell. The vacuum gauge is a good check. A seat of the pants feel would be going up an incline or if it is worse on a level road, you need to keep pushing down on the gas pedal more and more to keep the same speed. You could also get out and look at the cat after running a few min. like that and you would see it glowing red. I am glad you did mention just remove the o2 sensors and you will notice a drastic improvement right away. Lot of great interesting stuff in your videos-to much actually, it is 3 in the morning and I am still excited watching your videos, I need to get to sleep-lol.
Lol better than being addicted to crack I guess.
Hey, EXCELLENT video. And I like your style. Say, I'm at my wit's end here. Got a 91 Buick Century, which will start and run for about 10 minutes and then die, and won't start again until it's been sitting for a long time. It's not overheating, fuel pressure is good, just changed the fuel filter, sparks/coils all good, tested ignition module -- also good, changed air filter, ran diagnostic (OBD 1 so not real sophisticated), and only code I get is 26 which is "quad driver module circuit," which I believe controls things like the fan/what have you. I thought for SURE it's _GOT_ to be the cat, but just tested exhaust pressure with an exhaust back pressure gauge, and the result was that it stayed just around zero psi at idle, and somewhere around 1 psi at high rpms (though the gauge arrow will jump up to around 7 if you gun it in short spurts).
ANY THOUGHTS??? Possible suggestions? I'm not even sure what to try or look at at this point.
What is the fuel trim indicating while running and when it dies!
Schrodingers Box
Can you read fuel trim on an OBD1?
Yes you can. LTFT is Called "block learn" and STFT is called "integrator"
Schrodingers Box
Are these read with a scan tool?
Schrodingers Box
Here's the deal, my man. In the list of all possible OBD1 codes specific to my particular vehicle (2 digit codes from 13 to 66, which you can see here: www.troublecodes.net/GM/89-91_33N_mfi/ ) do not include anything about running rich or lean. So how could I possibly know what my fuel trims are? Is it even _possible_ on my model?? (
I am having a somewhat similar issue, but more difficulty diagnosing. I do have a graphic scan tool. I have a '00 GMC K3500 pickup with the 5.7 Vortec motor. I have one hallowed out catalytic converter and I plan on cutting the other one out in the near future (my state does not require emissions inspection). I had an exhaust leak from the exhaust "donut gaskets" on both manifold sides. I replaced both gaskets. About a week after the replacement, I got a code P0134 (low activity H1B1 02 Sensor). My truck has absolutely no power. It will go up to 65, but it takes forever to get there. On my scan tool, I noticed that the mv for bank 1 sensor 1 and bank 1 sensor 2 both fluctuate between very high numbers between 450 and 900mv. On bank 2, the sensor 1 number is always high while the sensor 2 number is always around 47 to 60mv . With my limited knowledge of exhaust systems I assumed the bank 2 sensor 2 was broken or the cat was clogged.
Long story short, watching this video, I feel like maybe it really is just a bad o2 sensor that's causing my extreme power loss?
I don't know what data do you have that shows its "just a bad O2 sensor"? What are your fuel trims? What variables were introduced to validate O2 response?
I would need to see some data.
@@SchrodingersBox I don't think I can share photos via youtube, however both long and short term fuel trims are 0 which I believe is perfect. I don't have an actual wideband so I cannot determine real time Air-Fuel Ratio. I did order a fuel pressure test kit, but I don't suspect fuel delivery is the issue.
The engine has no misfires per the scan tool. The only suspicious data on the scan tool was the o2 sensor readings for bank 1. It's strange to me that this happens after I finally "fixed" my exhaust leaks. My presumptions are; now that I've finally fixed the leak, air has no way to travel but through the cat which may have been clogged all along, or that the o2 sensor wire may have melted? I will try to check for continuity on the o2 sensor on the truck, but I'm at a loss.
Is there a part two? id like to see the restriction
There is not- I didn't film the replacement of the catalytic converter since thats pretty basic bolt-on stuff. But the cat was melted into an almost solid brick
@@SchrodingersBox Oh wow! thanks for sharing that part, and it ran well after I take it?
Yes it did. In fact, it ran so well after the repair that the next day the owner, not being used to the new power and responsiveness, lost control of the car during a snowstorm and totaled it lol. True story.
@@SchrodingersBox Whoa! lol..
I bought a exhaust back pressure kit. I dont think my problem is exhaust blockage, I wish it were. im afraid I may need a transmission :(
Good stuff!
One possible reason you didn't see scan data that time,could be because the car wasn't up to operating temperature,and was still in 'open-loop' mode. Once the O2 sensors and coolant,etc. get up to temp,the ECU/PCM (whatever you want to call it) should kick-in,and take over..and you should start seeing data. Thought it was worth a mention..might help explain the 'missing' scan data?
One test for plugged exhaust,is to pull the pre-cat O2 sensor(s) and see if it improves with them out. But then again,lots of hot exhaust gasses coming out of everywhere is a pretty good clue! :)
I once ran across a plugged cat. on an '86 Firebird - A V8 shouldn't be that gutless!
Hi again Phatty, glad you seem to be enjoying the channel! This communication issue with the scantool is actually just the result of having a $400 scan tool instead of a $4000 or even $10k scantool. It occassionally just drops communication and you have to actually reboot the laptop to get it to work again and i just didnt have time to do that. Its frustrating and often happens when i am doing test drives and stuff. Oddly, using a screen capture program while running AutoEnginuity invariably causes the same issue so It makes recording data for later use in videos impossible. Someday.... a Verus.... someday!
Ahh,gotcha. At least it's better than working 'blind' without any scan tool! (kind of impossible really,on newer cars.)
I've been working on cars since the 1970's. Former Master ASE tech. You use logic and common sense in your diagnosis. What is wrong with you? Just kidding, I am thoroughly impressed with you.
Thank you for the compliment!!
i just found this was my problem with my blazer.... anyway i am 90% sure this is main issue... black plugs,no power,bogs down when i give it gas...I replaced everything else you mentioned... my fingers are crossed...to make sure i will test back pressure in morn... thax
Once I had a truck died situation. When I stopped for a red light and went to go, it died. Once I popped the hood and saw the exhaust manifold glowing bright orange I knew what had happened. However, I had no symptoms leading up to the failure. Once it was confirmed, the fix was easy. Blocked Catalytic converter.
Now, I am driving a 94 F150 5.0 AT as opposed to an 88 F250 5.7 5 Spd ( the truck that got blocked cat) Having worked my way through testing the various components , EGR, MAF, IAC, Throttle Position Sensor, etc and vacuum lines, I am mostly sure I am doing things right and believe thus far all is within spec. Yet, I still have a mostly smooth idle, but have gotten a harder to start and keep running scenario. The main symptoms that caused me to need to diagnose things is the more prevalent and more frequent loss of power and sputtering/bucking type behavior when I go to accelerate up a hill or get up to speed like getting on the highway etc. In addition, I get the loss of acceleration and the knocking sound of like when the timing is retarded too far when going up hills etc. But this clears up when trans is in neutral and at idle or even when given pedal. As it sits, I am attempting to rule out the simple causes like old, bad or loose plug wires, cats, etc. Thanks for your teachings and demos. I am doing my best with OBD1 limitations and my own learning curves.
another great video!!
I also thought catalytic converter ...very nice step by step
Hello I'm five minutes into the video stopped looking diagnosed catalytic converter by what you said curious to finish watching video to see what you find thank you for your help .
Hi Matt
Arr, well at least I'm thinking in the right way so I must be getting some of this. Thanks a lot and I really appreciate your time in educating us. Thanks a bunch.
u r a man of integrity +:)
i remember first entering the automotive world, wondering was i crazy that so many “master techs” had no clue what they were talking about “you need all 4 oxygen sensors” on my crown victoria lean codes on both banks, i remember thinking i was crazy, cleaned the maf, car ran like a champ. never questioned myself again
Sir, I love your content! I find it very informative and entertaining. Thank you.
Awesome video.... thanks so much for actually showing and explaining the diagnosis
I did not see the vacuum gauge drop it looked steady to me while the engine was reving. Now maybe i am looking at the numbers backwards like the needle going up on the gauge is higher and down on the gauge is lower vacuum pressure. Anyways I just wanted to point that out.
I like your common sense approach I think you are a good teacher and you are humble enough to not let your ego get in the way of your learning. You have great videos man good luck.
Micscience The vacuum did indeed drop when the engine was revved. The needle swings back to the right, toward zero.
Great video on exhaust restriction. Again, your videos make more sense than others. There's always the teacher that matches better how a student thinks. I'm glad I found you and I'm glad you share videos.
Don't feel bad about listening to the alternator. I laughed. My mom has those cars and she's about the same age as this car owner. Can I say that? lol. Anyway, it's a resonant point of sound, and even though I know it doesn't mean anything, I always have to look at it when looking under her hood playing, find that sound.
"I need telemetry for my bunghole"
*honks three times*
"Are you threatening me?"
For second, at the end note... I genuinely had the image of a dead "cat" (meow) in the muffler... lmao.
Been a mechanic for 38 years and I have never let a customer pay for my mistake. Put that kind of pressure on yourself and you will become a great troubleshooter in a very short time or you go out of business.
Hahaha true that!!!!
ive had recent dramatic success with cleaning out the CATS: I drilled a small hole in the exhaust just before the CAT and while the engine is warm and running, I spray bursts of CARB CLEANING via a straw into the hole. (I do both sides- since I have a GMC van w 2 cats...) The drivability change is very pronounced! I use an entire can. I used a can of intake cleaner also once - w PEA.
I don’t follow- how can drivability increase? Catalytic activity has nothing to do with drivability. What drivability improvement are you experiencing?
If you get a Haynes manuel it will show you what the needle on the vacuum gauge will do when certain conditions exist.
It's generally considered that exhaust systems have 1.5psi max, anything over is considered a clog, higher than 3psi is alot.
Vacuum gauges are very good tool to diagnose a exhaust restriction I use it all the time
Do any cars monitor the pressure in the exhaust either directly or indirectly? Is there a trouble code for high exhaust pressure? What are typical codes that might get triggered when the exhaust is restricted?
The shop paying for things if they are wrong is exactly the kind of incentives structure needed for shops to not screw over customers or jerk them around, lying, dodging, coming up with new diagnoses, all at the customer's expense.
The auto repair industry has an incentives problem.
That's my diagnosis
This happened to my dad's 06 Altima V6 and it killed the engine. It took me 2 weeks to diagnose (Luckily I learned from you not to throw the parts at it until i'm sure :)
The front pre-cat fell apart and clogged the exhaust completely. I guess under huge pressure some of those pieces were sucked in by the engine (too close to exhaust ports) and it killed cylinders #2 and #4. Compression on #2 was 75, #3 was 90 while the other 4 cylinders were all at 145/155 (dry/wet test).
Believe it or not the car still pulled hard (AFTER we changed the cat) but smoked like a chimney. He had to add 1 quart of oil every other day.
We had to replace the engine.
Mickey Bauer That's unfortunate but good calkl. Yes, running the car in this condition can be quite damaging. I actually had another one come in since this video- but by the time the person brough it in, the engine was making a terrible pinging sound and it turned out to have no compression in a cylinder clearly due to a broken valve.
excellent vid! question: could a blocked CAT CON (or muffler) create a LEAN condition, misfires? thanks