Persistent Multi-Cylinder Misfire Issue
 

I have a multi-cylinder misfire issue that just won't go away.

Vehicle: 2005 Porsche 997.1 Carrera S, 80k Miles

Symptom:
Check Engine, Visit Workshop
Misfire Issue: Cylinders 1, 3, and 5
Codes: P0300, P0301, P0303, P0305

Data logging with a durametric cable indicates the cylinder misfires disappear once the car warms up.

Up until this point I've replaced the following components:

- AOS
- New Bosch Spark Plugs (May switch to NGK) & Coilpacks
- Crank position sensor
- Cam position sensors
- MAF
- VarioCam Conponents (Actuator Valve & Actuator Camshaft on both sides)
- Reflashed ECU to recommended latest release

Local shops that have worked to diagnose this issue with no success:
Bergman Autowerks - Replaced crank position sensor
Porsche Tysons Corner - Recommended replacing VarioCam components
Auto Sport Systems Group - Flashed the ECU

Each time I've replaced a component and cleared the codes they come back within 500 miles of driving.

I'm about to throw in the towel on this car. Any ideas on what I should do next are greatly appreciated. :bang:

Consider visiting Matt de Maria at Stuttgart Engineering in Gaithersburg. He is a master at sorthing out things like this.

(he's on Dorkiphus as well -- his name is also his user name)

Matt is the man!!!! Hands down agree!!

Stuttgart Performance Engineering

Address: 423/E E Diamond Ave, Gaithersburg, MD 20877
Phone: (301) 948-6762

Matt is an engineer. And he thinks like an engineer. As has been posted here many times, my first experience with him was regarding a significant problem that had been plaguing my previous car for FIVE years despite 4 other shops looking at it including months in one of them. Matt thought about it, then tried one thing (<2 hours of labor, no parts) and the car was fixed.

Have you checked the fuel pump? Perhaps it is not putting out full pressure.

Are your O2 sensors working?

Thanks for the suggestion guys. I'll reach out to Matt tomorrow to setup an appointment.

I had a similar issue on the lexus and it was caused by the timing belt being one notch off (was my own doing). Not sure it applies and don't know enough about all the pieces you have changed already to determine if there may be a similar cause...could the timing chain be off one notch?

Have you checked cam timing? 1, 3, 5, is all the same bank. I'm no expert, but I've heard of cam timing being off causing full bank mis-fire codes on M96/M97.

Can't speak for Chris, but I get a different set of cylinders every time across both banks, anywhere from 3 to all 6 at a time. Car runs and drives perfectly, and its is wildly intermittent. From my looking around, its seems there may be a number of early 997 owners with this issue

Based on this diagram 1, 3, and 5 are not on the same bank.

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