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Discussion Starter · #1 ·
I have a 2008 Cayman S. It has had occasional misfire problems. I solved an overheating problem by cleaning the crud that had accumulated between the radiators and the condensors--a problem that my local Porsche dealer was incapable of finding despite the existence of a service bulletin describing the failure. I then started using O'Rellly octane enhancer ($2.99 per bottle) in my car because here in California we can only obtain 91 octane gasoline. That really helped. Now I am noticing a new phenomenon.

I have noticed that when I have driven the car at high speeds for 45 minutes or so and I inadvertently step on the accelerator when the engine is operating below its optimal torque curve, e.g. I forgot to downshift, the car knocks and the CEL light comes on. Sometimes it just goes away. Other times it blinks and says "take the car to the workshop". In the extreme case, it sounds like it is running on five cylinders. If you drive the car for any distance in that condition, it dies. Shut the ignition off, restart the car and it runs just fine.

Now I can understand the car complaining and knocking when I demand low-end torque from an engine which has none. (I spent my formative years driving American V8s. With a Porsche, you have to pay attention.) I would expect the car to complain about a misfire and then turn the light off when everything is back in the groove. I do not expect the ECM to shut off a cylinder. Nor do I expect to have to "reboot the engine" to get it to run smoothly again.

As a precaution, I have ordered new coil packs and plugs and I am just going to shotgun the whole ignition system with new stuff. On my Durmetric I am seeing P0301 and P0303, so the packs are suspect and probably should be replaced anyway.

My question is this: Is there a software revision to the ECM that cures this behavior? At this point I don't trust my dealer to do anything unless I give them explicit instructions.


David Emberson
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