Good to see you again Duane. Cam and crank sensors are needed open or closed loop, the PCM is always looking for those reference signals so I don’t think open/closed loop is a factor here. But sensors can work fine cold and flake out when they get hot. The bouncing tach is a clue. My next quick diagnostic would be to get the vehicle to stall, spray the crank sensor with circuit freeze, and try starting again. If it starts right up you got your diagnosis.
Great to have you back, Duane! First off the bat I'd get it back to the shop and check for codes, and I'd spend a few more minutes trying to show an abnormality while in neutral. I'd do a quick inspection looking for obvious issues, fluids and drivetrain. So far we've shown a problem only under load, pointing to a fuel delivery problem, a drivetrain issue, or perhaps an ignition/spark delivery problem. I'd probably start with checking fuel pressure under load, to look for a pressure sag that might happen if the fuel pump is unable to deliver volume under conditions of high demand. In your videos I often see people guessing one specific cause, and they don't seem to realize, that's not the point. You're looking for a professional systematic approach that will consistently and efficiently lead to an answer, every time.
spelunkerd your so right. It's not the first guess that does much good. Critical thinking involves first understanding the system, taking any starting points we have and thinking how they can be related to the findings.
Hey Duane, Just wanted to say a couple things. First, I love this approach, very well done sir! The next is for your watchers, you must start and always consider the basics. I know it is very hard sometimes but, try to not get too deep until the basics are established. Keep up the great stuff my friend, Mark
As a retired senior master tech.with Ford Motor Co., I would like to say your skills and professionalism are outstanding. "I tip my hat to you sir".I sincerely hope all these young technicians will appreciate the knowledge your offering.
I'm not sure if this car has it but I would check for ignition module acting up after the engine warmed up also cam and crk sensors I would check those with a scope I don't think its fuel pump related cause it started and ran good cold but I would still check pressure if it was easy to do, That was a great tool at the end of the video but my only concern was it flexing a lot under pressure
Dear Duane, I've watched all of your vids since the beginning of yr channel. They have been very informative and enjoyable and you have always impressed as a nice guy interested in teaching others. This interactive approach has great potential. All that being said, I was especially nervous and concerned for you when I noticed that you weren't wearing your seatbelt during the video. Please do everything you can to help protect yourself - your subscribers want you to get the chance to make more great videos.
I would check the ignition, plug wires, coil/module. Then verify fuel pressure under load and possibly check the fuel pressure regulator. Next I'd check the temp of the catalytic converter input and output to verify the converter isn't clogged. Test computer for internal problems.
Well here's my thoughts on this. From what I've seen in this video, I would suspect either a fuel supply problem, or an RPM input problem, with fuel delivery being the prime suspect. Definitely need to pull codes first because there could be other problems that may or may not be related to the driveability problem. After that, the reason I would check for a supply problem first is because the bulk of the problem seems to happen under driving conditions. Fuel supply problems often manifest themselves under conditions when more engine power is needed, such as accelerating or climbing up a hill. Idling and even brake torquing do not put enough stress on the fuel supply system to uncover an intermittent problem in the fuel supply system. It's kinda-sorta like pedaling a bicycle with the back wheel off the ground. Anyway, a good preliminary test for this would be with the scan tool still hooked up, go for a test drive while looking at the pre-converter O2 sensor(s). If, when the car starts acting up, the pre-converter O2 sensor(s) are stuck at a low voltage as long as the cars acting up, low voltage being defined as below 450mv on a conventional O2 sensor, then a fuel supply problem can be further investigated. I would delve into this further Duane, but I've got some important business to take care of in the morning, so I need to get some sleep. Good to see you back again.
I've seen symptoms like this from insufficient fuel pressure, while the load is significant enough. I've seen failed MAFs cause problems like this. I personally haven't seen it yet, but I know crank sensors report to the fuel pump, "yeah, go ahead and pump". Cam shaft sensors can cause similar symptoms. Sometimes a engine code will point you one way or the other. If there is no engine code help then you just have to check if those sensors are working/have good wiring. I've even seen symptoms like this from poorly connected battery terminals. I had that happen to me on a cross country trip. I was like, crank sensor not sensing in the middle of the night? No, no, I saw on my scan gauge voltage dropping occasionally a little during the trip. That's what it was. Phew . . . felt like transmission issues too, lol.
i would want to see primary ignition waveforms to see if there is a loss of control to any of the coils. i would also like to check fuel pressure and make sure it is correct and stable. i would want to make sure the timing chain is in sync and tight by looking for any difference in where the spark occurs in realation to tdc compression. next i would want to check for large vacuum leaks espescally near the mass airflow sensor. then i would check the spark plug wires and plugs see if there is any leakage through the coating. i would also like to ensure the fuel filter is not clogged and restricing the flow. these are some things i would check first before spending time visually checking the timing chain or leaking heads.
A few more questions, does the car do this only in cold damp weather? Was the gas tank full of fuel when it sat over night? Sometimes moisture will form in the air void in the fuel tank. If the fuel is ok and a can of moisture remover (heat) is added and the problem persists perhaps check the the engine idle bypass that allows the EGR valve to stay open or open intermittently allowing to much air to enter the intake manifold. Does that model have single point fuel injection or multi-port injection? If you remove the air cleaner duct and squirt a small amount of fuel into the intake when it won't start and if it starts up then most likely the problem is in the fuel supply system.
I've had bad spark plug wires cause stumble on acceleration, but could be other reason too cause of the hard to start when warm, Also had partially bad crank sensor cause some of that on a Nissan Altima. And this looks like a good place to start cause it not be any of my above ideas Quote "spelunkerd 6 hours ago Great to have you back, Duane! First off the bat I'd get it back to the shop and check for codes, and I'd spend a few more minutes trying to show an abnormality while in neutral. I'd do a quick inspection looking for obvious issues, fluids and drivetrain. So far we've shown a problem only under load, pointing to a fuel delivery problem, a drivetrain issue, or perhaps an ignition/spark delivery problem. I'd probably start with checking fuel pressure under load, to look for a pressure sag that might happen if the fuel pump is unable to deliver volume under conditions of high demand. In your videos I often see people guessing one specific cause, and they don't seem to realize, that's not the point. You're looking for a professional systematic approach that will consistently and efficiently lead to an answer, every time."
Hi, The first thing I would do is grab my scanner on the first test drive or befor the test drive to give me a idea what should happen or any related symptoms that will occur to the code that appears. The reason I do this procedure first to every car is because knowing the code and the related system that code might monitor can give me a better state of mind of area I need to focus on.
Since this video is just a verification of a customer complaint more information is needed. Check engine light is a good place to start. Depending on the results from that would be where to head next. If no codes are present a lab scope reading of the cam and crank signal (and visual inspection of associated wiring while hooking up) would be the next step, followed by the same test/inspection of the O2 circuit(s). This test could be partially bypassed by monitoring whether the car is in open loop or closed loop during the condition. Fuel pressure would be the next step, followed by exhaust flow and emissions test. Doing an emissions test can help determine if the CAT is working efficiently, and if the ignition system is working as well. Of course if there are cylinder misfire codes you would go directly to that cylinder and check air/fuel/spark at the cylinder first.
Hi Duane, I am retires now but spent 45 years working on cars, wonder if the tachometer drops right down or is stable when it cuts out, indicating ignition problem, apart from that I would prob check for fault codes and fuel pressure, and change the fuel filter, the fact it runs pretty well sometimes indicates its nothing terminal I would say....and seems to be running on all cylinders.....might change the spark plugs...Fred in England.
First check for codes, check basic engine parameters while the condition is present like fuel trims, o2 signals, cam/crank signals, etc., check if any work has been done in the past that can relate to this problem, if there's nothing obvious check fuel pressure at load if you can.
As sort of an apprentice tech, wouldn't the crank and cam sensors also affect the engine under load, during the stall test, as well? Same with fuel, now that I think about it? I do know, cause I have experienced a bad TPS to be the cause of bucking while trying to shift gears even stalling in the road, and failing to shift along with high engine reving, cause the computer can't tell the transmission what it's doing. Though, it's not mentioned in the video that any transmission shifting is an issue.
hats off to you guys, this is the first time i watch a video that ends with an ad and doesn't get ruined with a single dislike :) and that was due to the great job you provide. for the evidence it seems to be a sensor that's responsible also for information feeding to ecu for the rev output, either CKP / CMP ?
This seems to be a fuel delivery problem. In order to start an engine you need fuel, air, spark, and compression. Take away any one of those and you'll stall out. I'd be interested in to see if the CEL is on and what the code(s) is/are. I'd also check the fuel pressure under idle, with the gas pedal pressed, and then trying to restart after a stall.
It could be either a fuel pump low pressure or clogged fuel filter or chocked exhaust catalytic converter that intensifies when engine became hot, or from a large vacuum leak that shows up after the car reaches operating temp since fuel delivery is rich when engine is cold, possibly such leak could be from a brake booster.
You don't advise if the check engine light is on while the car is running..??? The fact that it appears that you lose the tach signal when trying to start is important - the tach runs off of the read-back from the spark, so if no tach jumping when trying to start, no electric signal, and loss of something in the spark circuit - the ECU is then not getting the spark reading.
Even though the car ran ok in park, while cold; before it warmed up, was it bucking when you pulled out and started the driving test? Or did the bucking only begin, when it reached operating temperature during the test? Has me leaning towards exhaust (cat,o2) related, but I say that assuming it ran, in drive, fine before reading OT. Tach acting crazy may be caused by a low charge, from not turning over & continued cranking. This is fun!
I actually have this problem and I'm out of ideas on what it could be. I noticed that the fuel pressure regulator was leaking fuel out of the vacuum port so I replaced that but still have the same problem. So then I swapped out the ECM with one from a junk yard and that didn't help. So I did the same thing with the MAF and TPS sensor, the "boost sensor" (my car has that instead of a BARO sensor) but still the problem remains. There are no vacuum leaks, the ignition system is inspected and good and the fuel pump is replaced (when the fuel pressure regulator failed it also caused the one-way reed valve in the fuel pumps to fail). The timeing is right on the mark aswell. As you can see I did everything and still have the same problem.
So pitching that thing into the river isn't an option then? Oh well... So it starts up and runs okay at idle, but the second you put a load on it - it falls on its face. Hard starting when hot too. Not a vacuum leak - vacuum leak is the other way around. I'd check it for codes naturally - then maybe start with fuel?
Rule one of problem diagnosis - start with the most simple issue first. Then move up the food chain as it were... To me, the initial issues were a very accurate reflection of what I had in my Suzuki Grand Vitara... The loss of power, the lack of drive and so on. That turned out to be a simple fix - replaced MAF sensor in the air intake, just after the air filter on the 04 TD model in the UK and Europe. That said, I would consider other more advanced issues elsewhere as some behaviour isn't 100% consistent with just that fault. However, due to much of the similarities and the fact it's a real quick, easy job (you just pop the hood - everything you need to access is there), I would still consider it.
As it ran ok when cold it would be in open loop. Perhaps a coincidence but it seems like it started when entering closed loop. In that case it may be starving for fuel if lets say a O2 sensor is pegged rich which would cause a lean condition. The bouncing tach on the other hand is indicating a totaly different problem. I.e cam or crank sensor faulty. Heat problems usually take a bit longer to show up than a mile and in that case it is strange that it start and runs fine for a few minute if there is something wrong with the cam or crank.
Awww crap how did I miss this one starting 3 days ago. So far it only notified me when video 3 came out in my subscription feed. :( Noticing the tach signal issue would likely lead me in the direction of verifying mechanical timing (specifically ending up with a close look at timing advance), checking crank sensor wire to verify the sensor wire is good and CKP signal is good. I don't think it's going to be starter related because you can't hear it freewheel from lack of engagement (which could cut out the tach signal). Starter sounds good and it's trying to start. So tach signal (CKP) needs to be looked at eventually. Sounds as good of a place to start as any.
Since you mentioned the Tach and it was bouncing all over the place, then not registering at all, It seems like that could be the cam or crank sensor, or the wiring to them. But the first thing might best to try and pull up fault codes before going any further.
I changed plugs on neighbors vitara very worn out. 6 coil packs and no leads ? I have never worked on these and i need to test ignition coils. All 6 are from ebay ( cheapies) is it possible you can tell me resistance value on primary side and secondary side? I cant find a workshop manual or how to test a three pin coil with multimeter? Any reply appreciated
It looks like some kind of fuel starvation. the cols start was in open loop, so the cause can be foulty temp sensor or oxigen sensor, or fuel system not supplying the demand because of foulty pump or pressure regulator. less likely is clogged injectors
I'm leaning towards ignition problem. I don't think fuel because it started cold good. In my experience plugs and wires act up on excel, and he said it was wet out (maybe some arcing happening). Pretty easy anyway as a first start.
A bad fuel pump will often do that. Idle fine but under a load die out. The check engine lights would show up if the sensors were a problem. I would check for trouble codes. Then pressure test the fuel pump.
I'm no car mechanic by any stretch of the imagination but I have heard of similar symptoms before from floating debris in the fuel tank. At idle, things are fine but as fuel is drawn at a greater rate, the debris is sucked toward the fuel-line where it then blocks the intake. The engine craps out and dies, the debris is released from the intake and the engine can be started again only for the cycle to repeat a little later. I'd certainly be checking the tank with a boroscope and the fuel-line and pump to ensure that fuel was flowing properly in the absence of any computerised diagnostics tools I would probably then check the air intake and filter, too. If that did not yield any clues, that's the point at which I'd probably take it to a professional.
I would check fuel pressure first then condition of spark. With the no power a exhaust backpressure test on the cats or cat. I also would of never left the shop with a vehicle running so poorly. If I did it would leave the shop on a scan tool watching the upstream or upstreams o2s and verifying if it is really a lean condition. To the new guys a lean condition would be a fixed low signal around 100 to 200 millavolts.
Crank sensor on some cars like Toyota 5vzfe engine you can spay with water from a water bottle just a few squirts if it gors away momentarily then your crk sensor is no good
I'm a hobbyist not an apprentice or professional. -First I would check for codes, but since there's no info given I would start eliminating problems, -I would like to rule out the fuel system by doing an injector balance test and fuel pressure by doing snap throttle tests to see if the fuel pump can keep up under load. -with a scope would like to see what the TPS and MAF looks like, perhaps even clean the MAF sensor since its easy to get to. -My next move would be to seek a more experienced person for insight.
need help. .I'm a apprentice tech who is trying to figure out starting issues with my 1999 vitara. scanned and got code po340 and changed out the sensor after doing so the vitara still cranks with no start. checked for fuel as spark got neither. could the crankshaft sensor be the problem.
Duane, with so little info in front me, best guess, and that's all it is, is maybe VCT solenoid is stuck in the advanced position! For those who do not know that is a PCM controlled hydraulic solenoid that controls cam timing.
Hi everyone, Lets look at what we have Car runs fine at idle so vacuum is most likely not the issue. My fist clue is that I see that tack dropped out when trying to restart the car. So I would check the cmk and the crk sensors. (Get. wire diagram as I am not use to this vehicle…. ) I didn’t see the engine light on so I am guessing no codes I would test by back propping each sensor and see what I get, if I don’t have my ref signal I would un plug all sensors one ant a time to see if my reference signal comes back, that is to say all the sensors that share the same reference sig. DOC……
***** I just went back and looked at the video < Didn't see it at first , but you are right I think its on as well, so would also look for codes and freeze frame as well.... Thanks good catch!!!!!
Michael Doc Even though the light is not on, you should still check for codes and check all your readings for a lead to the problem.If you go from symptom to system to component to cause. You will come to your conclusion .
camshaft or crankshaft sensors, depending on which it learns about engine rpms... or the sprocket/balancer the crankshaft is learning from. English is not my mother language so sorry if there are errors
Crankshaft position sensor? I've replaced two of these on Saabs in the past couple years. The car will run fine if it's cold, but if you make a few short stops... car refuses to start. This seems like it could be the issue here, especially considering the tach is going nuts.
Hello, I am a tech who will be starting off in the field after graduating school. Since tje problem is only apparent under load, I would suspect a fuel delivery problem, or an ignition problem as well. Maybe the cam/crank sensors are not reading properly since the tach was all over the place so that would be a great place to start. Also, I would also look at the timing to see if it was ok. I would start probably with checking fuel pressure under load or doing an injector balance test first and then work my way to the other systems I suspect.
Oh, and with all the open/closed loop talk going on... Do we know that it's an issue when in open or closed mode? It seems to run fine at all times in park, or at a stop idling. Be a good question to ask duane... Does the motor rev fine in park, above 2000 rpm? does it only buck and jerk at 20 mph or more? while coasting? Duane? (oh, and love the material, excellent source of information, and enjoy the critical thinking it makes me do)
my suspect would be ckp and cmp. because while throttling or accelerating the ecu goes into open loop mode (accroding to my knowledge). This is also lead to tacho reading going haywire.
since everyone else already mentioned checking codes and stuff. based on the way the car presented the problems I would first look for a loose ground wire, body ground or maybe loose power wire somewhere in the engine compartment. maybe varmits been chewin.
With it getting worse with warming up leans me toward o2 sensors, but the bucking stops me at cps possibly usually they won't even start with bad crk sensor in my experience. With tach goofy, is there a place in the harness where there is some severe chafing(worn through a couple wires, ground maybe for all the above), or someone was working on it before and left something unplugged? Need diagram and to see dtc's.
Hi good day i have a 2008 Suzuki grand vitara and i park it for 4 weeks when i came back the battery was dead, so i got a jump start from my friend but after getting started i find out the engine wasn't revving out or it wasn't accelerate, my my mechanic check the airflow and the timing and the problem still wasn't fix. Am guessing that the car as lose it memory
Might be fuel delivery or ignition or maybe egr related problem letting in exhaust gasses at the wrong time.The fact that it idles ok seems to rule out cam and crank sensors.
I have a 2003 xl7 and having the same issue. test it with my scanner and it saying a camshaft position sensor. I thought first my transmission went bad. I do you adjust the timing is I install a new cps?
Assuming it has no codes, I'd check for spark when warmed up. If that was good, I'd next add some propane to the intake to check for a fuel issue. this sounds almost like the old GM injectors of doom that would fail when hot (Scannerdanner did a video on those) although I could see an ignition issue causing a similar problem.
CHECK AND SEE IF YOUR CHECK ENGINE LIGHT HAS ANYTHING TO DO WITH FUEL MAPPING . WHEN ENGINE IS COLD YOUR IN OPEN LOOP [FIXED TABLES] YOU MAY HAVE A MAF PROBLEM THAT SHOWS UP WHEN YOU GO INTO CLOSED LOOP OR LIKE OTHERS SAID IT MAY BE FUEL VOLUME .TIME TO START TESTING
My holden commodore had same problem with jerking under load after new ign module and coil packs it was worse took plugs out and badly worn , replaced plugs works great now
Given that it was okay cold I'd say it's a fueling issue, first step I would say is to check fuel pressure under load, because at low load / no load it seems to be fueling fine. The step before that would actually be to do a simple scan to make sure there's no codes & check mode 6 data while you're in there to see if anything failed. Also, it was wet, does it do this in the dry as well? If not, it's likely an ignition issue. Assuming fuel pressure is fine under load & it does it in the dry & no hidden codes I'd be interested in the crank position sensor due to the fluctuates in the tach while trying to start it. It may be nothing, but the connection or sensor could be bad which would explain the problems as the timing would have to advance enough to have power under load. If it doesn't there would be lack of ignition, which would cause bucking.
I will look for codes first, current and impending. Then I will watch the Fuel Trims while the car is coughing, this will tell me if enough fuel is supplied. RPM gage jumping will point to drop out of crank sensor, but cranks sensor normally does not have soft failure, it will not allow the car to start. My first guess is fuel, since it runs fine idling, next will be some coil not able to fire under load. If your scanner can show mode 6 data, that will be wonder full to see which sensor is misbehaving.
Well with just the information you've given us and with out running the codes or any information from the owner such as when was the last time it had anything done to it and such I would guess some kind of sensor issue maybe maf or related, but the rpm gauge and the fact that it ran fine until getting warmed up has me scratching my head some what I would probably disconnect the maf to see what happens first again if i didn't have any other information on the car.
My car does this sometimes it works ok and like u said jurks alot ive changed plugs and wont go up hills ive checked ht leads looks fine but when I touch the wire it gives a shock so any ideas please
Hi Duane I have a Susuki Forenza 2008. the head lights stay on when the car is turned off and and depletes the battery. I replace the turn signal multifuntion lever for a new one and everything stays the same. 😕. I check each fuse of the instrument panel fuse block and it was okay I also check the engine compartment fuse block and it's also okay. the battery : it's new and it's okay. 😨can you please help me solve this problem?
Hello Brigette, the head lights on that vehicle operate thru a "head light" switch. So, either the switch is bad and/or the wire from the headlight switch is shorted to power. Also, there is a recall on that switch. Check with your dealer and you may get it fixed for free.
also i think it might be a cam or crank sensor problem due to the rpm gauge doing that funny movement while cranking the engine also could be a fuel issue, maybe maf sensor
Love to see data pids!!watch for fuel and inputs..but it seems that when cold start fines.seen that on crank sensor when they retract and expand on temperture..and fuel pressure just by the simptoms!.will see!love video like this!
Hmmmm....Dirty/faulty MAF sensor maybe ? Over sensing, translating to over fueling. Heavy soot at tail pipe ? Might cold start ok due idle flair/IACV initial open position leaning the mix. Check MAF value on scan tool for invalid/erratic value swings.Disconnect MAF to default to MAP to confirm ?.....Can not square my theory with the erratic TACH though. Nice channel Thanx.
crank or cam sensor problem, being as how when cold it runs fine (open loop) and when its hot it runs crap (closed loop) would lead me to believe a sensor issue and the erattic rpm gauge tells me cam or crank sensor cuz the computer uses those to display rpm
based simply on the history of the zuki 2.0l engine & given those symptoms the cam position sensor or it's circuit are prime suspects. it's smart to look into an engine's history first.
Looks like it run rich because it works fine when engine is cold. I think spark plugs are wet & black. Also it can be oxygen sensor. I think you should check oxygen sensor readings first. P.S. I think it is not vacuum issues because idle is smooth and very low. BTW low idle and slow throttle responce is another evidence of rich mixture.
you have not said anything about engine light which normal takes us away from sensors. maybe low fuel pressure but it starts and runs. not electrical, not fuel so what else water in the fuel, kinda like that but not. the water is in a cylinder, a leaking head gasket and water goes out the exhaust. use a fiber cam to look inside the cylinders for water. the head is not cracked because it was you'd have some water in the oil. sounds crazy don't it but it happens
I thought it to be a crank or cam position sensor since I know that in some cases these sensors will prevent the car demonstrating and actually dying. Scan it
mine keeps squeling ,alternator is new belt is new . it's really starting to piss me off I've done everything possible to correct this I am sure it's a ground wire messed up. it's not worth the work involved to be honest
The way it was bucking reminds me of a plugged catalytic converter which cld be consistent with heat however I have had a Chrysler Pacifica once that had a broke wire/ missing five volt ref to the map sensor do the same thing as plugged cats, also when u showed the tach coming and going makes me think crank signal problem, maybe cam depending on design but most rpm signals are off the crank, def. gonna be heat related with a crank sensor or maybe a coolant leak that's present with pressure/hot engine and leaking on crank sensor. That's my initial 2 cents otherwise obviously check for codes and all that jazz before u get your hands dirty...
Good to see you again Duane.
Cam and crank sensors are needed open or closed loop, the PCM is always looking for those reference signals so I don’t think open/closed loop is a factor here. But sensors can work fine cold and flake out when they get hot. The bouncing tach is a clue. My next quick diagnostic would be to get the vehicle to stall, spray the crank sensor with circuit freeze, and try starting again. If it starts right up you got your diagnosis.
Great to have you back, Duane!
First off the bat I'd get it back to the shop and check for codes, and I'd spend a few more minutes trying to show an abnormality while in neutral. I'd do a quick inspection looking for obvious issues, fluids and drivetrain. So far we've shown a problem only under load, pointing to a fuel delivery problem, a drivetrain issue, or perhaps an ignition/spark delivery problem. I'd probably start with checking fuel pressure under load, to look for a pressure sag that might happen if the fuel pump is unable to deliver volume under conditions of high demand.
In your videos I often see people guessing one specific cause, and they don't seem to realize, that's not the point. You're looking for a professional systematic approach that will consistently and efficiently lead to an answer, every time.
spelunkerd your so right. It's not the first guess that does much good. Critical thinking involves first understanding the system, taking any starting points we have and thinking how they can be related to the findings.
Hey Duane,
Just wanted to say a couple things. First, I love this approach, very well done sir!
The next is for your watchers, you must start and always consider the basics. I know it is very hard sometimes but, try to not get too deep until the basics are established.
Keep up the great stuff my friend,
Mark
As a retired senior master tech.with Ford Motor Co., I would like to say your skills and professionalism are outstanding. "I tip my hat to you sir".I sincerely hope all these young technicians will appreciate the knowledge your offering.
I'm not sure if this car has it but I would check for ignition module acting up after the engine warmed up also cam and crk sensors I would check those with a scope I don't think its fuel pump related cause it started and ran good cold but I would still check pressure if it was easy to do, That was a great tool at the end of the video but my only concern was it flexing a lot under pressure
GREAT TOO SEE BACK DUANE GLAD YOU HAVE SOME NEW VIDEO
Dear Duane, I've watched all of your vids since the beginning of yr channel. They have been very informative and enjoyable and you have always impressed as a nice guy interested in teaching others. This interactive approach has great potential. All that being said, I was especially nervous and concerned for you when I noticed that you weren't wearing your seatbelt during the video. Please do everything you can to help protect yourself - your subscribers want you to get the chance to make more great videos.
I would check the ignition, plug wires, coil/module. Then verify fuel pressure under load and possibly check the fuel pressure regulator. Next I'd check the temp of the catalytic converter input and output to verify the converter isn't clogged. Test computer for internal problems.
Well here's my thoughts on this. From what I've seen in this video, I would suspect either a fuel supply problem, or an RPM input problem, with fuel delivery being the prime suspect. Definitely need to pull codes first because there could be other problems that may or may not be related to the driveability problem. After that, the reason I would check for a supply problem first is because the bulk of the problem seems to happen under driving conditions. Fuel supply problems often manifest themselves under conditions when more engine power is needed, such as accelerating or climbing up a hill. Idling and even brake torquing do not put enough stress on the fuel supply system to uncover an intermittent problem in the fuel supply system. It's kinda-sorta like pedaling a bicycle with the back wheel off the ground. Anyway, a good preliminary test for this would be with the scan tool still hooked up, go for a test drive while looking at the pre-converter O2 sensor(s). If, when the car starts acting up, the pre-converter O2 sensor(s) are stuck at a low voltage as long as the cars acting up, low voltage being defined as below 450mv on a conventional O2 sensor, then a fuel supply problem can be further investigated. I would delve into this further Duane, but I've got some important business to take care of in the morning, so I need to get some sleep. Good to see you back again.
I've seen symptoms like this from insufficient fuel pressure, while the load is significant enough.
I've seen failed MAFs cause problems like this.
I personally haven't seen it yet, but I know crank sensors report to the fuel pump, "yeah, go ahead and pump". Cam shaft sensors can cause similar symptoms. Sometimes a engine code will point you one way or the other. If there is no engine code help then you just have to check if those sensors are working/have good wiring.
I've even seen symptoms like this from poorly connected battery terminals. I had that happen to me on a cross country trip. I was like, crank sensor not sensing in the middle of the night? No, no, I saw on my scan gauge voltage dropping occasionally a little during the trip. That's what it was. Phew . . . felt like transmission issues too, lol.
water in ECU after rain surging when accelerating and shorting terminals .
i would want to see primary ignition waveforms to see if there is a loss of control to any of the coils. i would also like to check fuel pressure and make sure it is correct and stable. i would want to make sure the timing chain is in sync and tight by looking for any difference in where the spark occurs in realation to tdc compression. next i would want to check for large vacuum leaks espescally near the mass airflow sensor. then i would check the spark plug wires and plugs see if there is any leakage through the coating. i would also like to ensure the fuel filter is not clogged and restricing the flow. these are some things i would check first before spending time visually checking the timing chain or leaking heads.
Crank/camshaft sensor. The jumping rpm needle is the giveaway.
Fuel pressure is most likely ok since the torque loading was ok.
Probably I'll check for catalytic converter it's not clogged and the o2 sensor if it works fine... with the vaccum gauge from the intake vaccum.
A few more questions, does the car do this only in cold damp weather? Was the gas tank full of fuel when it sat over night? Sometimes moisture will form in the air void in the fuel tank. If the fuel is ok and a can of moisture remover (heat) is added and the problem persists perhaps check the the engine idle bypass that allows the EGR valve to stay open or open intermittently allowing to much air to enter the intake manifold. Does that model have single point fuel injection or multi-port injection? If you remove the air cleaner duct and squirt a small amount of fuel into the intake when it won't start and if it starts up then most likely the problem is in the fuel supply system.
I've had bad spark plug wires cause stumble on acceleration, but could be other reason too cause of the hard to start when warm, Also had partially bad crank sensor cause some of that on a Nissan Altima.
And this looks like a good place to start cause it not be any of my above ideas
Quote "spelunkerd 6 hours ago
Great to have you back, Duane! First off the bat I'd get it back to the shop and check for codes, and I'd spend a few more minutes trying to show an abnormality while in neutral. I'd do a quick inspection looking for obvious issues, fluids and drivetrain. So far we've shown a problem only under load, pointing to a fuel delivery problem, a drivetrain issue, or perhaps an ignition/spark delivery problem. I'd probably start with checking fuel pressure under load, to look for a pressure sag that might happen if the fuel pump is unable to deliver volume under conditions of high demand. In your videos I often see people guessing one specific cause, and they don't seem to realize, that's not the point. You're looking for a professional systematic approach that will consistently and efficiently lead to an answer, every time."
Hi,
The first thing I would do is grab my scanner on the first test drive or befor the test drive to give me a idea what should happen or any related symptoms that will occur to the code that appears. The reason I do this procedure first to every car is because knowing the code and the related system that code might monitor can give me a better state of mind of area I need to focus on.
Since this video is just a verification of a customer complaint more information is needed. Check engine light is a good place to start. Depending on the results from that would be where to head next. If no codes are present a lab scope reading of the cam and crank signal (and visual inspection of associated wiring while hooking up) would be the next step, followed by the same test/inspection of the O2 circuit(s). This test could be partially bypassed by monitoring whether the car is in open loop or closed loop during the condition. Fuel pressure would be the next step, followed by exhaust flow and emissions test. Doing an emissions test can help determine if the CAT is working efficiently, and if the ignition system is working as well. Of course if there are cylinder misfire codes you would go directly to that cylinder and check air/fuel/spark at the cylinder first.
Hi Duane, I am retires now but spent 45 years working on cars, wonder if the tachometer drops right down or is stable when it cuts out, indicating ignition problem, apart from that I would prob check for fault codes and fuel pressure, and change the fuel filter, the fact it runs pretty well sometimes indicates its nothing terminal I would say....and seems to be running on all cylinders.....might change the spark plugs...Fred in England.
First check for codes, check basic engine parameters while the condition is present like fuel trims, o2 signals, cam/crank signals, etc., check if any work has been done in the past that can relate to this problem, if there's nothing obvious check fuel pressure at load if you can.
As sort of an apprentice tech, wouldn't the crank and cam sensors also affect the engine under load, during the stall test, as well? Same with fuel, now that I think about it? I do know, cause I have experienced a bad TPS to be the cause of bucking while trying to shift gears even stalling in the road, and failing to shift along with high engine reving, cause the computer can't tell the transmission what it's doing. Though, it's not mentioned in the video that any transmission shifting is an issue.
hats off to you guys, this is the first time i watch a video that ends with an ad and doesn't get ruined with a single dislike :) and that was due to the great job you provide.
for the evidence it seems to be a sensor that's responsible also for information feeding to ecu for the rev output, either CKP / CMP ?
This seems to be a fuel delivery problem. In order to start an engine you need fuel, air, spark, and compression. Take away any one of those and you'll stall out. I'd be interested in to see if the CEL is on and what the code(s) is/are. I'd also check the fuel pressure under idle, with the gas pedal pressed, and then trying to restart after a stall.
It could be either a fuel pump low pressure or clogged fuel filter or chocked exhaust catalytic converter that intensifies when engine became hot, or from a large vacuum leak that shows up after the car reaches operating temp since fuel delivery is rich when engine is cold, possibly such leak could be from a brake booster.
Heat related component breakdown. Cam/crank sensor as an initial suspect. Time for the scanner and some live data.
You don't advise if the check engine light is on while the car is running..??? The fact that it appears that you lose the tach signal when trying to start is important - the tach runs off of the read-back from the spark, so if no tach jumping when trying to start, no electric signal, and loss of something in the spark circuit - the ECU is then not getting the spark reading.
Even though the car ran ok in park, while cold; before it warmed up, was it bucking when you pulled out and started the driving test? Or did the bucking only begin, when it reached operating temperature during the test?
Has me leaning towards exhaust (cat,o2) related, but I say that assuming it ran, in drive, fine before reading OT. Tach acting crazy may be caused by a low charge, from not turning over & continued cranking.
This is fun!
Darren G. It ran normally at cold start up, then after a moments ( less than an mile) it bucked and jerked.
I actually have this problem and I'm out of ideas on what it could be. I noticed that the fuel pressure regulator was leaking fuel out of the vacuum port so I replaced that but still have the same problem. So then I swapped out the ECM with one from a junk yard and that didn't help. So I did the same thing with the MAF and TPS sensor, the "boost sensor" (my car has that instead of a BARO sensor) but still the problem remains. There are no vacuum leaks, the ignition system is inspected and good and the fuel pump is replaced (when the fuel pressure regulator failed it also caused the one-way reed valve in the fuel pumps to fail). The timeing is right on the mark aswell. As you can see I did everything and still have the same problem.
Oh yeah, I also replaced the crank and cam sensors from a junk yard with no success.
What about the catalytic converter.
So pitching that thing into the river isn't an option then? Oh well...
So it starts up and runs okay at idle, but the second you put a load on it - it falls on its face. Hard starting when hot too. Not a vacuum leak - vacuum leak is the other way around. I'd check it for codes naturally - then maybe start with fuel?
Rule one of problem diagnosis - start with the most simple issue first. Then move up the food chain as it were...
To me, the initial issues were a very accurate reflection of what I had in my Suzuki Grand Vitara...
The loss of power, the lack of drive and so on.
That turned out to be a simple fix - replaced MAF sensor in the air intake, just after the air filter on the 04 TD model in the UK and Europe.
That said, I would consider other more advanced issues elsewhere as some behaviour isn't 100% consistent with just that fault.
However, due to much of the similarities and the fact it's a real quick, easy job (you just pop the hood - everything you need to access is there), I would still consider it.
As it ran ok when cold it would be in open loop. Perhaps a coincidence but it seems like it started when entering closed loop. In that case it may be starving for fuel if lets say a O2 sensor is pegged rich which would cause a lean condition. The bouncing tach on the other hand is indicating a totaly different problem. I.e cam or crank sensor faulty. Heat problems usually take a bit longer to show up than a mile and in that case it is strange that it start and runs fine for a few minute if there is something wrong with the cam or crank.
Awww crap how did I miss this one starting 3 days ago. So far it only notified me when video 3 came out in my subscription feed. :( Noticing the tach signal issue would likely lead me in the direction of verifying mechanical timing (specifically ending up with a close look at timing advance), checking crank sensor wire to verify the sensor wire is good and CKP signal is good. I don't think it's going to be starter related because you can't hear it freewheel from lack of engagement (which could cut out the tach signal). Starter sounds good and it's trying to start. So tach signal (CKP) needs to be looked at eventually. Sounds as good of a place to start as any.
Since you mentioned the Tach and it was bouncing all over the place, then not registering at all, It seems like that could be the cam or crank sensor, or the wiring to them. But the first thing might best to try and pull up fault codes before going any further.
I changed plugs on neighbors vitara very worn out. 6 coil packs and no leads ? I have never worked on these and i need to test ignition coils. All 6 are from ebay ( cheapies) is it possible you can tell me resistance value on primary side and secondary side? I cant find a workshop manual or how to test a three pin coil with multimeter? Any reply appreciated
It looks like some kind of fuel starvation. the cols start was in open loop, so the cause can be foulty temp sensor or oxigen sensor, or fuel system not supplying the demand because of foulty pump or pressure regulator. less likely is clogged injectors
I'm leaning towards ignition problem. I don't think fuel because it started cold good. In my experience plugs and wires act up on excel, and he said it was wet out (maybe some arcing happening). Pretty easy anyway as a first start.
A bad fuel pump will often do that. Idle fine but under a load die out. The check engine lights would show up if the sensors were a problem. I would check for trouble codes. Then pressure test the fuel pump.
I'm no car mechanic by any stretch of the imagination but I have heard of similar symptoms before from floating debris in the fuel tank. At idle, things are fine but as fuel is drawn at a greater rate, the debris is sucked toward the fuel-line where it then blocks the intake. The engine craps out and dies, the debris is released from the intake and the engine can be started again only for the cycle to repeat a little later.
I'd certainly be checking the tank with a boroscope and the fuel-line and pump to ensure that fuel was flowing properly in the absence of any computerised diagnostics tools I would probably then check the air intake and filter, too. If that did not yield any clues, that's the point at which I'd probably take it to a professional.
I would check fuel pressure first then condition of spark. With the no power a exhaust backpressure test on the cats or cat. I also would of never left the shop with a vehicle running so poorly. If I did it would leave the shop on a scan tool watching the upstream or upstreams o2s and verifying if it is really a lean condition. To the new guys a lean condition would be a fixed low signal around 100 to 200 millavolts.
Crank sensor on some cars like Toyota 5vzfe engine you can spay with water from a water bottle just a few squirts if it gors away momentarily then your crk sensor is no good
I'm a hobbyist not an apprentice or professional.
-First I would check for codes, but since there's no info given I would start eliminating problems,
-I would like to rule out the fuel system by doing an injector balance test and fuel pressure by doing snap throttle tests to see if the fuel pump can keep up under load.
-with a scope would like to see what the TPS and MAF looks like, perhaps even clean the MAF sensor since its easy to get to.
-My next move would be to seek a more experienced person for insight.
need help. .I'm a apprentice tech who is trying to figure out starting issues with my 1999 vitara. scanned and got code po340 and changed out the sensor after doing so the vitara still cranks with no start. checked for fuel as spark got neither. could the crankshaft sensor be the problem.
Duane, with so little info in front me, best guess, and that's all it is, is maybe VCT solenoid is stuck in the advanced position! For those who do not know that is a PCM controlled hydraulic solenoid that controls cam timing.
Hi everyone,
Lets look at what we have
Car runs fine at idle so vacuum is most likely not the issue.
My fist clue is that I see that tack dropped out when trying to restart the car.
So I would check the cmk and the crk sensors. (Get. wire diagram as I am not use to this vehicle…. )
I didn’t see the engine light on so I am guessing no codes
I would test by back propping each sensor and see what I get, if I don’t have my ref signal I would un plug all sensors one ant a time to see if my reference signal comes back, that is to say all the sensors that share the same reference sig.
DOC……
Michael Doc I think that top middle light was the check engine light.?.
***** I just went back and looked at the video < Didn't see it at first , but you are right I think its on as well, so would also look for codes and freeze frame as well.... Thanks good catch!!!!!
Michael Doc I like the way you think thru the problem. Thanks for adding your comments
Michael Doc Even though the light is not on, you should still check for codes and check all your readings for a lead to the problem.If you go from symptom to system to component to cause. You will come to your conclusion .
I've notice the tech doesn't jump up or down when cranking. have not tested compression yet. any advise would be helpful.
camshaft or crankshaft sensors, depending on which it learns about engine rpms... or the sprocket/balancer the crankshaft is learning from.
English is not my mother language so sorry if there are errors
Crankshaft position sensor? I've replaced two of these on Saabs in the past couple years. The car will run fine if it's cold, but if you make a few short stops... car refuses to start. This seems like it could be the issue here, especially considering the tach is going nuts.
Use scan tool to check for OBD-II fault codes. Check fuel pressure, possibly low. Change fuel filter, it might have partial blockage
Hello, I am a tech who will be starting off in the field after graduating school. Since tje problem is only apparent under load, I would suspect a fuel delivery problem, or an ignition problem as well. Maybe the cam/crank sensors are not reading properly since the tach was all over the place so that would be a great place to start. Also, I would also look at the timing to see if it was ok. I would start probably with checking fuel pressure under load or doing an injector balance test first and then work my way to the other systems I suspect.
Oh, and with all the open/closed loop talk going on... Do we know that it's an issue when in open or closed mode? It seems to run fine at all times in park, or at a stop idling. Be a good question to ask duane... Does the motor rev fine in park, above 2000 rpm? does it only buck and jerk at 20 mph or more? while coasting? Duane? (oh, and love the material, excellent source of information, and enjoy the critical thinking it makes me do)
my suspect would be ckp and cmp.
because while throttling or accelerating the ecu goes into open loop mode (accroding to my knowledge). This is also lead to tacho reading going haywire.
What does the ckp and cmp stand for?
crank shaft position sensor, cmp cam shaft position sensor.
Thank you
since everyone else already mentioned checking codes and stuff. based on the way the car presented the problems I would first look for a loose ground wire, body ground or maybe loose power wire somewhere in the engine compartment. maybe varmits been chewin.
With it getting worse with warming up leans me toward o2 sensors, but the bucking stops me at cps possibly usually they won't even start with bad crk sensor in my experience. With tach goofy, is there a place in the harness where there is some severe chafing(worn through a couple wires, ground maybe for all the above), or someone was working on it before and left something unplugged? Need diagram and to see dtc's.
What does cps stand for ?
cam position sensor, crk would be crank position
moisture possible causing a coil issue maybe, it may be arking cause a misfire type of condition.
Hi good day i have a 2008 Suzuki grand vitara and i park it for 4 weeks when i came back the battery was dead, so i got a jump start from my friend but after getting started i find out the engine wasn't revving out or it wasn't accelerate, my my mechanic check the airflow and the timing and the problem still wasn't fix. Am guessing that the car as lose it memory
from the given information I´ve vould suspect fuel and tryed to mesured a fuel presure but those RPM at the end cconfused me
I have a vitara it will start but it stall I change the MAF sensor it work for little time & then is doing it again i don't know what is wrong now
Might be fuel delivery or ignition or maybe egr related problem letting in exhaust gasses at the wrong time.The fact that it idles ok seems to rule out cam and crank sensors.
I have a 2003 xl7 and having the same issue. test it with my scanner and it saying a camshaft position sensor. I thought first my transmission went bad. I do you adjust the timing is I install a new cps?
Assuming it has no codes, I'd check for spark when warmed up. If that was good, I'd next add some propane to the intake to check for a fuel issue. this sounds almost like the old GM injectors of doom that would fail when hot (Scannerdanner did a video on those) although I could see an ignition issue causing a similar problem.
Fuel filter dirty?
CHECK AND SEE IF YOUR CHECK ENGINE LIGHT HAS ANYTHING TO DO WITH FUEL MAPPING . WHEN ENGINE IS COLD YOUR IN OPEN LOOP [FIXED TABLES] YOU MAY HAVE A MAF PROBLEM THAT SHOWS UP WHEN YOU GO INTO CLOSED LOOP OR LIKE OTHERS SAID IT MAY BE FUEL VOLUME .TIME TO START TESTING
My holden commodore had same problem with jerking under load after new ign module and coil packs it was worse took plugs out and badly worn , replaced plugs works great now
Could it possibly be a leaky fuel injector(s)?
start cold = closed loop ok
hot engine problems = ecm relies on sensors to run
You got it backwards - the EFI system runs open loop until the O2 sensor is warm enough to provide feedback and then goes into closed loop
Given that it was okay cold I'd say it's a fueling issue, first step I would say is to check fuel pressure under load, because at low load / no load it seems to be fueling fine. The step before that would actually be to do a simple scan to make sure there's no codes & check mode 6 data while you're in there to see if anything failed.
Also, it was wet, does it do this in the dry as well? If not, it's likely an ignition issue.
Assuming fuel pressure is fine under load & it does it in the dry & no hidden codes I'd be interested in the crank position sensor due to the fluctuates in the tach while trying to start it. It may be nothing, but the connection or sensor could be bad which would explain the problems as the timing would have to advance enough to have power under load. If it doesn't there would be lack of ignition, which would cause bucking.
is this a vvt engine? probably not but I had a guest come into my shop once with it stuck on and it did this exact same thing...worth looking at.
Going with o2 sensor. Plus check codes?
I would start by looking at scan tool pids like fuel trims and cam/ crank signals if available.
I will look for codes first, current and impending. Then I will watch the Fuel Trims while the car is coughing, this will tell me if enough fuel is supplied. RPM gage jumping will point to drop out of crank sensor, but cranks sensor normally does not have soft failure, it will not allow the car to start. My first guess is fuel, since it runs fine idling, next will be some coil not able to fire under load. If your scanner can show mode 6 data, that will be wonder full to see which sensor is misbehaving.
Of course I would check for codes to help bring me in to the right direction
Well with just the information you've given us and with out running the codes or any information from the owner such as when was the last time it had anything done to it and such I would guess some kind of sensor issue maybe maf or related, but the rpm gauge and the fact that it ran fine until getting warmed up has me scratching my head some what I would probably disconnect the maf to see what happens first again if i didn't have any other information on the car.
My car does this sometimes it works ok and like u said jurks alot ive changed plugs and wont go up hills ive checked ht leads looks fine but when I touch the wire it gives a shock so any ideas please
Hi there,
Did you find the problem?
Hi Duane
I have a Susuki Forenza 2008.
the head lights stay on when the car is turned off and and depletes the battery.
I replace the turn signal multifuntion lever for a new one and everything stays the same. 😕. I check each fuse of the instrument panel fuse block and it was okay I also check the engine compartment fuse block and it's also okay.
the battery : it's new and it's okay.
😨can you please help me solve this problem?
Hello Brigette, the head lights on that vehicle operate thru a "head light" switch. So, either the switch is bad and/or the wire from the headlight switch is shorted to power. Also, there is a recall on that switch. Check with your dealer and you may get it fixed for free.
Ok. 😊 thank you👏👏👏👏👏👍👍👍
Vacuum issues? Ignition? Camshaft sensors
I like your videos and how you teach...thanks
Sounds like a crank sensor to me, when it heats by engine heat it breaks down.
hi, is the cam sensor no work
perhaps a drop out in injector pulse or ignition caused by crank and can inputs.
It needs further information like DTC codes and live data from different sensor to look inside.
What does dtc stand for ?
phillip hall Diagnostic Trouble Codes if I am not wrong!
Thank you
also i think it might be a cam or crank sensor problem due to the rpm gauge doing that funny movement while cranking the engine also could be a fuel issue, maybe maf sensor
Cam position sensor or a throttle position sensor
Imma go with Crank sensor. Seeing what the rim gadge did there. May be a wire issue most likely a wire issue.
Love to see data pids!!watch for fuel and inputs..but it seems that when cold start fines.seen that on crank sensor when they retract and expand on temperture..and fuel pressure just by the simptoms!.will see!love video like this!
Hmmmm....Dirty/faulty MAF sensor maybe ? Over sensing, translating to over fueling. Heavy soot at tail pipe ? Might cold start ok due idle flair/IACV initial open position leaning the mix. Check MAF value on scan tool for invalid/erratic value swings.Disconnect MAF to default to MAP to confirm ?.....Can not square my theory with the erratic TACH though. Nice channel Thanx.
the crank or camshaft sensor because that the RPM was jumping when trying to restart. those sensors go like that when hot.
crank or cam sensor problem, being as how when cold it runs fine (open loop) and when its hot it runs crap (closed loop) would lead me to believe a sensor issue and the erattic rpm gauge tells me cam or crank sensor cuz the computer uses those to display rpm
based simply on the history of the zuki 2.0l engine & given those symptoms the cam position sensor or it's circuit are prime suspects. it's smart to look into an engine's history first.
Check the codes first. My first thought without codes, is fuel pressure or fuel injectors. Then spark.
Looks like it run rich because it works fine when engine is cold. I think spark plugs are wet & black. Also it can be oxygen sensor. I think you should check oxygen sensor readings first.
P.S. I think it is not vacuum issues because idle is smooth and very low. BTW low idle and slow throttle responce is another evidence of rich mixture.
. .exactly what mine is doing. . .trying to diagnose, I think it may be fuel filter (start cheap and easy)
you have not said anything about engine light which normal takes us away from sensors. maybe low fuel pressure but it starts and runs. not electrical, not fuel so what else water in the fuel, kinda like that but not. the water is in a cylinder, a leaking head gasket and water goes out the exhaust. use a fiber cam to look inside the cylinders for water. the head is not cracked because it was you'd have some water in the oil. sounds crazy don't it but it happens
I thought it to be a crank or cam position sensor since I know that in some cases these sensors will prevent the car demonstrating and actually dying. Scan it
mine keeps squeling ,alternator is new belt is new . it's really starting to piss me off I've done everything possible to correct this I am sure it's a ground wire messed up. it's not worth the work involved to be honest
I'd start at fuel pressure regulator, fuel pump and/or fuel filter and if they are ok, then exhaust system for a a blockage.
fuel pressure regulator has a torn diaphram
i would try cleaning the mass air flow or mass air pressure
The way it was bucking reminds me of a plugged catalytic converter which cld be consistent with heat however I have had a Chrysler Pacifica once that had a broke wire/ missing five volt ref to the map sensor do the same thing as plugged cats, also when u showed the tach coming and going makes me think crank signal problem, maybe cam depending on design but most rpm signals are off the crank, def. gonna be heat related with a crank sensor or maybe a coolant leak that's present with pressure/hot engine and leaking on crank sensor. That's my initial 2 cents otherwise obviously check for codes and all that jazz before u get your hands dirty...
not a whole lot of experience but I would start checking cam crank sensor signals looks like your crank signal was falling out or shorting
In my opinion. I would start with checking fault codes, I would say faulty maf or fuel pressure.
My thoughts are vacuum or fule