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THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHRough idle and CEL help needed
Reported or suspected cause
flywheel
Reported cause
No successful repair reported for this finding.
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Reported cause
Strange enough, for me it turned out to be the flywheel.
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Performed · outcome unconfirmed
It was either slightly imbalanced, installed improperly by under the care of the po, or came slightly lose.
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Performed · outcome unconfirmed · Original poster
OK Final verdict was most likely a sticking exhaust lifter as we only replaced the intake lifters 4 years ago.
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Performed · outcome unconfirmed · Original poster
Replaced just the #6 spark plug and made it worse!
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Performed · outcome unconfirmed · Original poster
This same right side we replaced the lifters on about 2 years ago and now the end of the camshaft falls out when trying to replace a lifter.
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Well, kind of stumped on where to go next on this one. My 02 C2 will run fine all day and then for no reason I get an intermitent rough idle. Most of the time after a few seconds it will fix itself without touching the throttle? Other times it will not until you get going to the next light and idle again...and its fine. When hot and idling in park you can induce it by bliping the throttle and most times it will fix itself again after a few seconds.
It will pop a CEL every once in a while and always misfire #6. So, replaced all the coil packs since the car has 98K on it. No difference. Cleaned the throttle body and MAF, no change. Replaced just the #6 spark plug and made it worse! Have had the Porsche computer on it and nothing really stands out. What might look bad for a while then goes away while reading the engine at idle.
Ideas appreciated.
Thanks
Try swapping coil packs to see if stumble/misfire follows.
Check/clean/swap fuel injectors.
Test compression/leak down.
Post the exact DTCs you are getting.
Misfire does not travel with the coil pack. Leak down heads where I am thinking, lifter going flat? But a spark plug change making it worse makes no sense. That is why I am stuck on electrical?? I have heard that on the MAF, may be it but a lot of money to guess with.
Thanks guys!
I had the same problem. The dealer tried everything common to a misfire (coil, plug, etc) and nothing worked. Had it in the shop four times.
Strange enough, for me it turned out to be the flywheel. It was either slightly imbalanced, installed improperly by under the care of the po, or came slightly lose.
The dealer replaced it under CPO and it finally resolved the mystery misfire.
Does it do it when cold? If not and only when hot, it might be a clogged purge valve that does not allow engine fumes to escape thus gas does not flow correctly. It throws no errors.
Or, gas lines?
Misfire on #6 and changing plug made it worse, coil pack no diffefence. I'd change the plug to another new one on #6
What code does this throw? Are you clearing the cel? Does it continually throw a cel and code?
I'd look at an injector. I'd think at idle it could cause a lean mixture and misfire only on one cylinder. Is condensation in fuel tank possible? Is fuel tank low? Try some Heet to displace moisture.
All good ideas. Next is fuel injector cleaner and heet as I have heard these before. It does only do it hot, the cold start sequence works fine. Thanks for the ideas!
The misfire error code is flagging a weak cylinder. If the misfire is not accompanied by a flashing CEL the misfire is due to a mechanical problem.
If you can with the Porsche computer you have disable the spark/injector fuel pulse to each cylinder in turn -- with the engine up to temp and idling -- and note the rpm drop.
Chances are high when you kill the #6 cylinder the rpms will drop less, indicating the #6 cylinder is not contributing as much to the engine's idle speed as the other cylinders.
The question then becomes 'why'?
What did the original #6 plug look like? I'd like to know what it looked like compared to the other plugs too. If it looks like it has been running 'hot' maybe an injector is weak and the misfires are due to a lean mixture.
If the plug is 'clean', this is a sign coolant is leaking into the combustion chamber. A head gasket failure, a crack in the head, or even a crack (D-chunk failure) is the likely cause.
A collapsed lifter should be considered, but this usually is accompanied by some noise, ticking. A flat lobe on the cam is another possibility.
If the engine has VarioCam Plus, the mechanism that provides the variable lift on at least one intake valve of one cylinder is suspect as well.
With the right Porsche computer you can activate the variable valve timing and lift feature per bank and probably eliminate or confirm there's a problem.
Sincerely,
Macster.
Thanks Macster Very helpful. The CEL never flashes so these are some good ideas. The plug was normal just the gaps were huge with 30,000 miles on it? No coolant loss and the car runs perfect off idle. Gas milage is down though about 1.7 mpg.
Well, just to finish this thread off, THE FREAKIN CAMSHAFT IS BROKEN! So goes the most dependable Pcar I have ever owned BS. This same right side we replaced the lifters on about 2 years ago and now the end of the camshaft falls out when trying to replace a lifter. Absolutely stupid.
Broken camshaft not likely as the engine would not run because the valves on the side with the broken camshaft would be hit by the pistons.
What has probably happened is the VarioCam at the end of the intake camshaft has failed. The cam still turns it is just the VarioCam feature on that side that doesn't work.
Generally I consider the last thing touched suspect and I note the lifters on that side were replaced, but 2 years ago is a long time and anything done wrong at that time should have manifested itself before now.
Regardless, the problem is not fatal and can be addressed -- I believe (hope anyhow) -- with the engine in the car.
Sincerely,
Macster.
That was my question is how was it even running. I will go by tomorrow and look at the pieces. Engine is still in the car. Cam is in Germany so it will be a few days. Thanks for the advice!
It could have been an expansion plug on the end of a camshaft that blew out.
Dharn had a similar thing happen to him, after putting too much pressure on the expansion plug with the cam lock down tool.
Nope, the cam was probably carcked and then came apart at the journal between 4 and 5 once unbolted. Unbelievable, and it has been 4 years almost 30,000 miles since the lifters were replaced on that side. Funny thing as we went looking for a used right side intake cam and there are none around....probably a good reason for this as there are plenty of left side ones?
This wasn't the idle problem so we are replacing all 4 lifters on #6. Can't make the missfire move to another cyclinder. At this point I just want a rough idle again!
Was the engine internals ever worked on before this incident?
I had my camshafts break on my bimmer but found out afterwards, PO worked on it and didn't torque down things properly.
OK Final verdict was most likely a sticking exhaust lifter as we only replaced the intake lifters 4 years ago. Really lucky this happened before the cam finished breaking into two pieces and ruining the motor most likely. So, one new intake cam also. A lot of money to spend on this car but it had to be done.
Hope nobody needs this thread in the future?
It had a broken camshaft
I got the car at a little less than 39,000 miles and in warranty. I am pretty sure the oil was being changed at the recommended intervals. I blame this on two lifter issues. What broke the cam, I / we have no idea?
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