Can someone check this

[bnewport]

I have a 99 C4 with Tiptronic. I've been getting check engine lights under the following conditions only.

Put the car in M, and select 2nd. Accelerate slowly up to around 6.4k rpm and then hold it there. My check engine light comes on after a few seconds. The P-codes are P300 + P301-5. It normally just misfires on 2 and 5 but I've seen misfires on 1-5.

I've have the car at the dealer, we've changed the valve lifters and the DME and it's still there. Porsche have given up for now as it's proving very hard to figure out whats wrong.

The current theory is that tip retards engine timing as it prepares to shift, my lifting to even throttle at 6.4k upsets it and the retarded timing is what causes a misfire.

I'm looking to see if other tiptronics have this problem or is it just me? If you can try it then it'd be interesting to see if this is a design issue or a fault in my car.

Billy

Edited November 1, 2005 by bnewport

[Loren]

Do you feel the misfire? You don't mention how the engine is actually running (regardless of the CEL).

If the engine runs good and you don't actually feel the misfire then I would think you may have a bad flywheel sensor.

[bnewport]

Do you feel the misfire? You don't mention how the engine is actually running (regardless of the CEL).

If the engine runs good and you don't actually feel the misfire then I would think you may have a bad flywheel sensor.

<{POST_SNAPBACK}>

The car feels perfect, if I taped over the light, I'd never know it came on. Flywheel sensor is a new one, I haven't heard that as a reason so far.

[Loren]

Have they put a scanner on it and graphed the O2 sensors and fuel trim numbers? Have they looked at the air flow over the MAF (graphed it) too?

You can disconnect the MAF and most folks wouldn't notice - until the light comes on.

Something is telling the DME that something isn't right and you should be able to see that on the scanner graphs.

[Eric (Plug Guy)]

One question, sort of unrelated....why hold it at 6400 rpm? You rev-happy?

:D

[bnewport]

Have they put a scanner on it and graphed the O2 sensors and fuel trim numbers? Have they looked at the air flow over the MAF (graphed it) too?

You can disconnect the MAF and most folks wouldn't notice - until the light comes on.

Something is telling the DME that something isn't right and you should be able to see that on the scanner graphs.

<{POST_SNAPBACK}>

They ran all the usual engine tests. They replaced spark plugs, swapped coils around, checked injectors. The PCNA guy was even over looking at it and they don't know whats wrong at this point. Whats the theory with the MAF related to the symptoms?

[Loren]

A CEL is caused by the DME saying that something is not within spec - emission wise. If they have have not graphed the O2 sensors, MAF and fuel trim then they are shooting in the dark. If they are all okay (which I doubt) then the problem must be mechanical or electro-mechanical (i.e. VarioCam).

[bnewport]

One question, sort of unrelated....why hold it at 6400 rpm?  You rev-happy?

:D

<{POST_SNAPBACK}>

You're on a track, a faster guy behind you wants to pass, you lift to let him by. If I'm doing 90ish in 3rd thats around this RPM.

It also happens when zipping in to highway traffic in 2nd, lift to find your slot and then squeeze in. You're holding the RPMs at this point.

Not too hard to do this...

Edited November 2, 2005 by bnewport

[bnewport]

A CEL is caused by the DME saying that something is not within spec - emission wise. If they have have not graphed the O2 sensors, MAF and fuel trim then they are shooting in the dark. If they are all okay (which I doubt) then the problem must be mechanical or electro-mechanical (i.e. VarioCam).

<{POST_SNAPBACK}>

The dealer checked the flywheel. Porsche called them this morning suggesting the data points to the drive shaft not being balanced, maybe a weight came off. We won't know till I bring the car in next.