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October 26, 2005

Check engine light update

I'll get the car back next week. It has new valve lifters and a new engine management computer (DME). The dealer ran all the engine tests and everything passes. So, the mystery of why the check engine light comes on remains a mystery. The symptom is that when the engine revs to high RPMs, i.e. around 6k to 6.5k and then you move to even throttle thus holding the RPMS at that level. After a couple of seconds, the light comes on. Examples of scenarios where this happens would be entering a highway ramp in second and then accelerating to 50 and then lifting to enter traffic.

The current theory at the dealer is that Tiptronic has already initiated shifting and is delaying the engine timing in antipication of a shift. But, when I lift and move to steady throttle then something goes wrong and a check engine light comes on. I wouldn't mind finding a document describing exactly how Tiptronic works. Another anomoly was that the dealer reckons Tip should shift at 6.7k RPM but I know I saw 7k - 7.1k when driving it at the DE. The rev limiter is supposed to be at 7.2k

Suspect parts are now knock sensor or a misaligned drive train, we don't know. Porsche North America basically said to take the car home as is and wait for the problem to 'worsen' so that the cause will then be clearer. They don't think they can diagnose the problem 100% right now so I need to wait for the problem to fester. They are hoping that it'll be easier to diagnose at that point.
The current OBD II codes are misfires on 2 and 5 with an occasional misfire on 3 but while misfires are reported, you wouldn't know it from driving the car, no physical symptoms at all besides the light.

Right now, I guess the good news is the engine passes all tests with flying colors. Nothing appears to be wrong with it at all. At 37k miles, the car now has new revised lifters giving it a whopping 300bhp instead of 296bhp and a new DME.

October 26, 2005 | Permalink


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