Interesting related story: in the previous generation Jetta with the 2.0 engine, the camshaft position sensor is inside the distributor housing. The distributor is driven by an "intermediate shaft" which is driven by the timing belt. If the sprocket for that intermediate shaft had skipped a tooth on the belt, the camshaft would still be fine and properly timed (thus no valve damage), however the ignition timing would be slightly off and the camshaft position sensor would not be triggered at the appropriate time, thus causing a code. Such was the case with my ex girlfriend's car when we first bought it used. While installing a new timing belt, some idiot had rotated the intermediate shaft a quarter turn plus a tooth or two (and moved the HT leads correspondingly), causing all kinds of issues, one of which was a camshaft code. Wish I'd been doing videos back then, as it was an interesting case study.
Great diagnosis job! And that's a good car in its way. Once I had to drive with one unit misfiring for some 200 km, another time I drove almost without oil in the sump (just about a kilometer or so) and the sucker is still on duty scince 1998! My mom rides it though)
Hi have seen this video since have been needing info on my Passat w8.. yesterday when i start the engine it made a tick,tapping sound for the first time. Well it's due for service in abt 1000 km...mileage 130k. We re happy for knowledge shared.
DE Nichols Indeed you are correct. I actually LOVE it that people keep me my toes and it pushes me to be complete and comprehensive. I just dont always have the time to dedicate for each video though.
Why MAF code? When the cam timing is off, the volumetric efficiency of the engine is lower. It's not as good as it should be at getting the air into the cylinders. The throttle will need to be open more to get the required air into the cylinders. Therefore the MAP will give a higher reading. The computer associates the increased MAP and a larger throttle opening with way more intake air flow than what has been measured. Hence the MAF code!
Simon Parkinson Brilliant! Absolutely makes sense, especially considering this vehicle is drive-by-wire which I never even mentioned in the video. Truly brill!!!!
+Schrodingers Box I wasn't about to try and explain my thought process related to the MAF, CMP correlation, because in the end my dumbed down theory would have made me look ignorant in the end, but this is essentially what I was picturing in my mind. The camshaft would have been off in timing, which would result in the valve timing being altered slightly, which in turn would alter the air pressure being measured by the air intake sensors, resulting in a MAF code. I may be misunderstanding some things, but that's what my thought process was when you started talking about a MAF code misunderstanding.
Are all the belts manufactured like that? For some reason, I thought the teeth would be integral part of the belt rather than being glued on as they seem to be in this case. If the teeth were molded in to, I would think it would be very hard for them to separate as they had done here.
12vgs8606 Yeah I cannot really explain that the teeth seem to break off so uniformly as opposed to wear uniformly. Not sure what was happening in there.
John David Anderson Thanks- it was interesting indeed. Seeing that belt almost makes you want to check the one in your own car before you go to bed lol
I would speculate for late timing the MAF code may not only due to less fresh air is the cylinder (the exhaust valve would still be open so it's drawing in the exhaust gases for start of intake stroke) but the intake valve being open for the compression stroke means a bunch of the fresh air (and exhaust) it breathed in goes back into the intake. I'd imagine this probably trips up the computer because of the O2 sensor going artificially lean with the fresh air introduced to the exhaust, the MAP (if it has one) would read higher intake manifold pressure because of the air being pumped back into the manifold on compression stroke, and who knows what kind of fuel compensation the computer would end up doing here (less oxygen in the cylinders cause of drawing in exhaust on the intake stroke and because exhaust ends up in the intake manifold, but oxygen being pumped into the exhaust) - would be fascinating to run the engine for a while to see what it does, but obviously that's way too risky.
112665 miles on my jetta and it started making a continuing ticking noise , very quiet but evry time I accelerate it gets loder and speeds up. I'm not sure about any timing belt change in its life. The check engine lit up 1 month before the ticking. Damn 2b honest, I'm scared to step on the gas evrytime I enter the freeway 😅
Same here for my step sons jetta !! But the noise is .ad loud so he stopped driving it (thank god) months ago and now months later he wants to fix it and it sounds like it got louder . Im not a mechanic, idk if its a easy/not too expensive fix or if he should just get rid of the kar. He thought it was so messed up and I showed him this video so he kan see its not as bad as it may sound and he should probably just get it fixed. He only had the kar for like 2 or 3 months before the noise started
On many EU vehicles the ECU calculates the timing from the Crank sensor and the Cam sensor to throw an engine light when the cam-belt stretches too much. Fiat have a specific dealer code for this in the Bosch ECU. It will actually throw the car into limp mode if it detects the belt has stretched but it only works if the dealer calibrates it when a brand new belt had been fitted. I have seen a stripped belt like that caused by a backfire from a leaking exhaust manifold. The MAF can also cause this same backfire if it makes it run rich but this can be seen obviously by a either a burnt out CAT, bad emission or even the flexi joint on the exhaust turns blue and melts, exhaust manifold leak can also burn out the flexi joint too. Sometimes the belt teeth just jump, common on VW as the tensioner corrodes badly to the point it stiffens/jams up, jumps a tooth and strips the belt. Never overlook the fact that this can also happen by over-revving the engine without any load on it, high engine rev when panicking on a hill start for some drivers. The amount of people i have seen blow up their engine revving the balls of it at traffic lights or in a car park showing off. Furthermore, dirt and gravel kicked up from the road that somehow finds it's way into the cam belt does the same thing too. Lots of variable some of which you can not test for. Moral of the story is, I would have never suspected the cam sensor and certainly not the cam shaft itself. The only way you can call a camshaft is by removing it and measuring the lobes and journals.
Well done Matt , I would have thought an 02 sensor code would have set but German engineering is so extreme you need extreme techs that fully understand their systems. Hey I have to give credit to the people that work on them everyday, HA - they probably find American cars odd to work on.
Steve Rob Yes I agree- I have no knowledge of the PCM strategy on a VW at all, and as you saw the CPS code came first and "stole" the freezeframe from the MAF so no help their on fuel trim. Because of the engine sound and nature of the belt condition I did not run the engine any more than needed to do investigation until I fixed the problem.
kuuuba777 In canada we dont have most European car brands , only American, German, and now Chrysler/Fiat. We did have , Renault, Citroen and Peugeot my favourite years ago. I wish we had cars from France again , i thought they were good cars.
The only thing that worries me a bit - you blamed tensioner as a couse of this belt issue. Um... Why? There are a few other pulleys touching the belt. Any evidence of broken tensioner? And what could have happened to cause this amount od thooth go away?
messer7bc Yeah I should have shown the broken tensioner, I obviously lost that in the editing. 146K miles on a 70K recommended timing service, I am satisfied the cause of the problem is apparent.
I bet when you put the timing belt on you have to be 1 tooth out so when you tension up the belt all the marks line up. I found this out when my dad and I done a timing belt on a TDI Passat and found this problem and resolved it by putting it out 1 tooth so the marks aligned when we tensioned the belt. We obviously done the 2 complete revolutions before starting the car up.
If the piston is on the intake stroke yet the valves are closed wouldn't the low pressure in the cylinder force both the intake and exhaust valves open a little to draw air from the intake manifold and the exhaust? Air coming in through the exhaust would not be measured. Or are the valve springs stronger than I think?
No the 20mmHg vacuum is not nearly enough to do that. Not by a longshot. But now you got me wondering if the negative pressure in that event might increase the draw of air when the intake does open. Hmmmmmm.
I have this sort of noise on my Audi A4 B7 2.0Tdi 170 but with an oil pressure light on. Strangely though the noise sometimes goes away when starting it then comes back the next time. Any ideas??
MAF sensor code - Inlet opens late so the descending piston will have built up a vacuum in it's cylinder. When the valve opens there is a big drop in inlet pressure which does not match the rpm. My 10 cents anyway. Hey I'm not a mechanic either, I'm a bio-engineer working with brain/computer interfaces so what do I know? Andy
"I don't know Volkswagens very well at all." That statement is very untrue. You understand the fundamental laws of physics and electromagnetism, and the rules of diagnosis and troubleshooting. You understand Volkswagens very well! :D What you're talking about here with the MAF code is entirely Manufacturer Logic(tm). The long strings of code programmed to look for presumed failure modes (IF statements) inherently builds a structure resulting in all other possibilities (ELSE statements). If a situation happens that the engineers and programmers never dreamed of (or just didn't feel like including), it can lead down a very bizarre trail of catch-all errors until it finds one that "fits," and sets it. Under identical circumstances, once manufacturer's vehicle sets a Pxxxx, while another sets a Pyyyy. That is, of course, a gross oversimplification of things, but hopefully it gets the point across. :)
rhkips Good point. When I said I don't know VW's well I was specifically referring to the PCM algorithms. On GM models, I am normally quite familiar with the criteria for setting the various codes and equally important, the variables that would NOT set a code or in fact prohibit the setting of other codes (e.g. an O2 sensor code will disable a catalytic converter code). But on VW's I've never had to look up such information so I don't have any "feel" for the algorithms. I was stunned to see the MAF code occur, frankly.
Again, Great!!!! but i would have to disagree on the MAF explanation. On VW a rich mixture in the exhaust would cause a rich mixture fault, not a MAF fault. Cheers!!!
+Nabil Chouchany It seems you misunderstood the operation of the MAF sensor to volumetric efficiency determination. Try watching the end of the video again and perhaps it will be clear.
+Schrodingers Box i did get your point on maf/volumetric efficiency. But i still don't think it would cause the code. I have worked on vw systems and motronic injection, and never have i seen this... Cheers!
Nabil Chouchany But we proved scientifically it did. WHat would your explanation be and what evidence basded support do you have for it that contradicts what we just saw in the video?
+Schrodingers Box You did prove it. And your explanation is very logical. I have worked extensively on many VW with this same engines, and other similar engines (same engine management), and i never saw a maf code triggered by faulty timing. Although these systems do trigger maf codes very commonly, but most commonly the PCV system is the culprit. It can reset and take time to show again (months sometimes), and eventually when the code sticks, you'll find the problem.. So i'm saying that your train of thought is very logical, but it doesn't necessarily coincide with the engine management fault detection algorithm (which many, many times is not). Cheers!
Rotf, I am always amazed at the nonchalant stuff people notice! Anyway I do love it. I spend a lot of time on my knees. Even more so when I work on a car.
Schrodingers Box Someday you'll be able to marry that boy down the street and I'll be able to marry my niece(yummy), hang in there buddy, our day is coming, thank the gay's for leading the way.....Yes ! Love wins !
joeandgod1 Well maybe I could marry that boy right now if you would just grant permission since you're his father. I know it's sick but I guess things with your dad just got old for me
Interesting related story: in the previous generation Jetta with the 2.0 engine, the camshaft position sensor is inside the distributor housing. The distributor is driven by an "intermediate shaft" which is driven by the timing belt. If the sprocket for that intermediate shaft had skipped a tooth on the belt, the camshaft would still be fine and properly timed (thus no valve damage), however the ignition timing would be slightly off and the camshaft position sensor would not be triggered at the appropriate time, thus causing a code. Such was the case with my ex girlfriend's car when we first bought it used. While installing a new timing belt, some idiot had rotated the intermediate shaft a quarter turn plus a tooth or two (and moved the HT leads correspondingly), causing all kinds of issues, one of which was a camshaft code. Wish I'd been doing videos back then, as it was an interesting case study.
Great diagnosis job! And that's a good car in its way. Once I had to drive with one unit misfiring for some 200 km, another time I drove almost without oil in the sump (just about a kilometer or so) and the sucker is still on duty scince 1998! My mom rides it though)
Hi have seen this video since have been needing info on my Passat w8.. yesterday when i start the engine it made a tick,tapping sound for the first time. Well it's due for service in abt 1000 km...mileage 130k. We re happy for knowledge shared.
I guess I'm just too trusting. The concerns of others surely made for an excellent video here. :) Great follow up video.
DE Nichols Indeed you are correct. I actually LOVE it that people keep me my toes and it pushes me to be complete and comprehensive. I just dont always have the time to dedicate for each video though.
perfect explanation of the timing being off thank you lol not very many people get that
Why MAF code?
When the cam timing is off, the volumetric efficiency of the engine is lower. It's not as good as it should be at getting the air into the cylinders. The throttle will need to be open more to get the required air into the cylinders.
Therefore the MAP will give a higher reading.
The computer associates the increased MAP and a larger throttle opening with way more intake air flow than what has been measured. Hence the MAF code!
Simon Parkinson Brilliant! Absolutely makes sense, especially considering this vehicle is drive-by-wire which I never even mentioned in the video.
Truly brill!!!!
+Schrodingers Box
I wasn't about to try and explain my thought process related to the MAF, CMP correlation, because in the end my dumbed down theory would have made me look ignorant in the end, but this is essentially what I was picturing in my mind. The camshaft would have been off in timing, which would result in the valve timing being altered slightly, which in turn would alter the air pressure being measured by the air intake sensors, resulting in a MAF code. I may be misunderstanding some things, but that's what my thought process was when you started talking about a MAF code misunderstanding.
Are all the belts manufactured like that? For some reason, I thought the teeth would be integral part of the belt rather than being glued on as they seem to be in this case. If the teeth were molded in to, I would think it would be very hard for them to separate as they had done here.
12vgs8606 Yeah I cannot really explain that the teeth seem to break off so uniformly as opposed to wear uniformly. Not sure what was happening in there.
that was a good and interesting job on the VW.
John David Anderson Thanks- it was interesting indeed. Seeing that belt almost makes you want to check the one in your own car before you go to bed lol
I would speculate for late timing the MAF code may not only due to less fresh air is the cylinder (the exhaust valve would still be open so it's drawing in the exhaust gases for start of intake stroke) but the intake valve being open for the compression stroke means a bunch of the fresh air (and exhaust) it breathed in goes back into the intake. I'd imagine this probably trips up the computer because of the O2 sensor going artificially lean with the fresh air introduced to the exhaust, the MAP (if it has one) would read higher intake manifold pressure because of the air being pumped back into the manifold on compression stroke, and who knows what kind of fuel compensation the computer would end up doing here (less oxygen in the cylinders cause of drawing in exhaust on the intake stroke and because exhaust ends up in the intake manifold, but oxygen being pumped into the exhaust) - would be fascinating to run the engine for a while to see what it does, but obviously that's way too risky.
yep that’s what I think too!
LOL @ the Arkansas joke
?Kirk S What joke? lol
Schrodingers Box ;-)
Damn what shop did you take it to? Sounds good.
112665 miles on my jetta and it started making a continuing ticking noise , very quiet but evry time I accelerate it gets loder and speeds up. I'm not sure about any timing belt change in its life. The check engine lit up 1 month before the ticking. Damn 2b honest, I'm scared to step on the gas evrytime I enter the freeway 😅
It actually waste a lot of gasoline. And in park. I don't mind doing a tune up to make sure its up to check. But to find a good mechanic is hard.
Same here for my step sons jetta !! But the noise is .ad loud so he stopped driving it (thank god) months ago and now months later he wants to fix it and it sounds like it got louder . Im not a mechanic, idk if its a easy/not too expensive fix or if he should just get rid of the kar. He thought it was so messed up and I showed him this video so he kan see its not as bad as it may sound and he should probably just get it fixed. He only had the kar for like 2 or 3 months before the noise started
On many EU vehicles the ECU calculates the timing from the Crank sensor and the Cam sensor to throw an engine light when the cam-belt stretches too much.
Fiat have a specific dealer code for this in the Bosch ECU. It will actually throw the car into limp mode if it detects the belt has stretched but it only works if the dealer calibrates it when a brand new belt had been fitted.
I have seen a stripped belt like that caused by a backfire from a leaking exhaust manifold. The MAF can also cause this same backfire if it makes it run rich but this can be seen obviously by a either a burnt out CAT, bad emission or even the flexi joint on the exhaust turns blue and melts, exhaust manifold leak can also burn out the flexi joint too.
Sometimes the belt teeth just jump, common on VW as the tensioner corrodes badly to the point it stiffens/jams up, jumps a tooth and strips the belt.
Never overlook the fact that this can also happen by over-revving the engine without any load on it, high engine rev when panicking on a hill start for some drivers.
The amount of people i have seen blow up their engine revving the balls of it at traffic lights or in a car park showing off.
Furthermore, dirt and gravel kicked up from the road that somehow finds it's way into the cam belt does the same thing too. Lots of variable some of which you can not test for.
Moral of the story is, I would have never suspected the cam sensor and certainly not the cam shaft itself. The only way you can call a camshaft is by removing it and measuring the lobes and journals.
Correction. Camshaft Position Sensor is CMP not CPS. Auto manufacturers specify CKP and CMP because otherwise both would be CPS.
***** Duly noted- I brain farted there
Well done Matt , I would have thought an 02 sensor code would have set but German engineering is so extreme you need extreme techs that fully understand their systems. Hey I have to give credit to the people that work on them everyday, HA - they probably find American cars odd to work on.
Steve Rob Yes I agree- I have no knowledge of the PCM strategy on a VW at all, and as you saw the CPS code came first and "stole" the freezeframe from the MAF so no help their on fuel trim. Because of the engine sound and nature of the belt condition I did not run the engine any more than needed to do investigation until I fixed the problem.
Steve Rob In Europe we have much more complicated cars than vws. Any french car will be nightmare to you if you find vws over engineered
kuuuba777 In canada we dont have most European car brands , only American, German, and now Chrysler/Fiat. We did have , Renault, Citroen and Peugeot my favourite years ago. I wish we had cars from France again , i thought they were good cars.
Steve Rob I have had 2 viewers from France claim the Renaults are the worst to work on ever!
The only thing that worries me a bit - you blamed tensioner as a couse of this belt issue.
Um... Why?
There are a few other pulleys touching the belt. Any evidence of broken tensioner?
And what could have happened to cause this amount od thooth go away?
messer7bc Yeah I should have shown the broken tensioner, I obviously lost that in the editing. 146K miles on a 70K recommended timing service, I am satisfied the cause of the problem is apparent.
I bet when you put the timing belt on you have to be 1 tooth out so when you tension up the belt all the marks line up. I found this out when my dad and I done a timing belt on a TDI Passat and found this problem and resolved it by putting it out 1 tooth so the marks aligned when we tensioned the belt. We obviously done the 2 complete revolutions before starting the car up.
Correct- on some models it's 2 or even 3 teeth to allow for adjustment on final tension setting.
You explanation makes sense to me but i'm a 2%'er, good video. I cant stand working on modern VW's.
Ozzstar You are indeed, thanks for your support bro!
2:40 Do you talk about the guy who insisted that the noise was piston slap [the valve]?;)
If the piston is on the intake stroke yet the valves are closed wouldn't the low pressure in the cylinder force both the intake and exhaust valves open a little to draw air from the intake manifold and the exhaust? Air coming in through the exhaust would not be measured. Or are the valve springs stronger than I think?
No the 20mmHg vacuum is not nearly enough to do that. Not by a longshot. But now you got me wondering if the negative pressure in that event might increase the draw of air when the intake does open. Hmmmmmm.
I have this sort of noise on my Audi A4 B7 2.0Tdi 170 but with an oil pressure light on. Strangely though the noise sometimes goes away when starting it then comes back the next time. Any ideas??
no sorry I would have to hear where it is coming from. could be PCV??
Great vids
MAF sensor code -
Inlet opens late so the descending piston will have built up a vacuum in it's cylinder. When the valve opens there is a big drop in inlet pressure which does not match the rpm.
My 10 cents anyway.
Hey I'm not a mechanic either, I'm a bio-engineer working with brain/computer interfaces so what do I know?
Andy
"I don't know Volkswagens very well at all."
That statement is very untrue. You understand the fundamental laws of physics and electromagnetism, and the rules of diagnosis and troubleshooting. You understand Volkswagens very well! :D
What you're talking about here with the MAF code is entirely Manufacturer Logic(tm). The long strings of code programmed to look for presumed failure modes (IF statements) inherently builds a structure resulting in all other possibilities (ELSE statements). If a situation happens that the engineers and programmers never dreamed of (or just didn't feel like including), it can lead down a very bizarre trail of catch-all errors until it finds one that "fits," and sets it. Under identical circumstances, once manufacturer's vehicle sets a Pxxxx, while another sets a Pyyyy.
That is, of course, a gross oversimplification of things, but hopefully it gets the point across. :)
rhkips Good point. When I said I don't know VW's well I was specifically referring to the PCM algorithms. On GM models, I am normally quite familiar with the criteria for setting the various codes and equally important, the variables that would NOT set a code or in fact prohibit the setting of other codes (e.g. an O2 sensor code will disable a catalytic converter code).
But on VW's I've never had to look up such information so I don't have any "feel" for the algorithms. I was stunned to see the MAF code occur, frankly.
This 2003 golf diesel makes a smacking noise on startup he is saying it's just a hanger for the exhaust is that possible?
Sure. anything is possible. Maybe its loose change under the carpeting. Could be anything.
Again, Great!!!! but i would have to disagree on the MAF explanation. On VW a rich mixture in the exhaust would cause a rich mixture fault, not a MAF fault. Cheers!!!
+Nabil Chouchany It seems you misunderstood the operation of the MAF sensor to volumetric efficiency determination. Try watching the end of the video again and perhaps it will be clear.
+Schrodingers Box i did get your point on maf/volumetric efficiency. But i still don't think it would cause the code. I have worked on vw systems and motronic injection, and never have i seen this... Cheers!
Nabil Chouchany But we proved scientifically it did. WHat would your explanation be and what evidence basded support do you have for it that contradicts what we just saw in the video?
+Schrodingers Box You did prove it. And your explanation is very logical. I have worked extensively on many VW with this same engines, and other similar engines (same engine management), and i never saw a maf code triggered by faulty timing. Although these systems do trigger maf codes very commonly, but most commonly the PCV system is the culprit. It can reset and take time to show again (months sometimes), and eventually when the code sticks, you'll find the problem..
So i'm saying that your train of thought is very logical, but it doesn't necessarily coincide with the engine management fault detection algorithm (which many, many times is not). Cheers!
What monster is 10 feet long and has 3 teeth?
The funnel cake line at the Arkansas state fair.
Ha!
nice knee pad. I have the same one.
Rotf, I am always amazed at the nonchalant stuff people notice!
Anyway I do love it. I spend a lot of time on my knees.
Even more so when I work on a car.
hi, ihave a jetta 4 1999 2.0 and the problem that i have is start the engine but when i press the gas it want o stop he engine.can you help me please
Yes what data do you have?
thanks but it was the maf sensor .it fell the resistence of the maf
Impossible. The MAP would compensate. Hopefully you didn't waste money replacing the MAF.
a friend of mine disconnect the maf and it work but i remove the maf and i notice that didnt have a resistor .because i look from other ,but thanks
Of course it worked without the MAF. That should be obvious as described in the video.
The MAF is not the issue.
Is AK the most deserving state? At least the color of the teeth matches :-)
12vgs8606 Winner winner chicken dinner!!! Made me spit my coffee up!!!
We need not necessarily just kushite like kids 9:00
I've never seen a timing belt loose it's teeth before, that owner was lucky.
So, you are an antiarkansasonian? An antidentite?
I am anti-hypodontia
@@SchrodingersBox Bill Clinton is probably pro-hypodontia. Especially when it comes to the extramarital front grill.
I'm from Arkansas
Sorry to hear that.
Just kidding just kidding!!
listen to my car engine only happins when car is hot
The Supreme Court gave you the right to marry yesterday,how does it make you feel? You celebrating?
joeandgod1 As usual your logic is incorrect. It is still completely illegal for me to marry a 12 year old. Epic fail as usual.
Schrodingers Box Someday you'll be able to marry that boy down the street and I'll be able to marry my niece(yummy), hang in there buddy, our day is coming, thank the gay's for leading the way.....Yes ! Love wins !
joeandgod1 Well maybe I could marry that boy right now if you would just grant permission since you're his father. I know it's sick but I guess things with your dad just got old for me
Schrodingers Box You don't drive a Miata do you? ;)
***** I do indeed. Every day. But, of course 'My Miata' is a nickname I give to JoeandGod1's mom.
Ohhh, burn!!