intermittent misfire on `06 carrera base model

[Ambro]

Purchased this `06 Carrera (997) Cabriolet with manual trans, about a year and a half ago. Early on, I started to experience intermittent misfires independent of speed, gear, or on freeway or surface street. Took it in to the Porsche Dealer who sold it to me, and they determined faulty ignition coils and spark plugs to be the source of the misfires. They also performed a Porsche multi-point inspection with satisfactory results. A few weeks later, the misfires started up again, and again I took it back to the dealer. A week later, I was notified by the dealer that they could not duplicate the symptom and could not identify the fault code to home in on the problem. I've driving the car for the past several months tolerating the same intermittent misfires. I really can use some help/advice.
Thank you

[keitho64]

If you have access to an ODBII Scanner, retrieve the code(s) and post them here. This will pinpoint what cylinder it is. It will also show if there are any O2 codes, injector codes, etc. Since the plugs/coils did not resolve the issue, it is possible a failing injector could be causing it, or something else. How many miles are on the car? Do you have any maintenance history on it?

[Ambro]

Keith,
Thank you for such a detailed response. Yes, I do have a scanner purchased several years ago and still in the unopened package it came in. This will give a novice like me a chance to learn how to use it and investigate future problems. I will work on it today and let you know the results. My car has 45900 miles on it and I do have the carfax showing the maintenance history.
Ambro

[keitho64]

If the air oil separator has not been replaced that could be an issue.

I have an 00 C2 with 57,000 miles. It would intermittently spit/sputter, like a misfire, but never trigger check engine light. It finally did about 1 month ago and it was an up stream O2 sensor. I bought 2 new O2 sensors but the error has not returned so I am just waiting.

My car had the plugs, coils, valve cover gaskets and AOS replaced at 51,000.

It is also possible you have a leaky valve cover gasket that is causing the coil to arc. You can check by removing each coil and see if there is oil on them. If there is, I would bet that is the issue.

[Ambro]

Check performed using OBDII resulted in "No Codes." Review the history of maintenance, all with the dealer, history showed the vehicle was serviced at the required intervals, and the maintenance inspections performed at the time of each service were satisfactory. There were no significant mechanical repairs done throughout its lifetime other than front brake/brake light bulb replacement. Tires were replaced every 4-5 years, and the battery was replaced twice. Since I bought the car in May21, I replaced the battery, and all the spark plugs and ignition coils as a result of first reporting it to the dealer.

[Ambro]

Thanks for your input on the other possible culprits. I will work on them or refer them to my mechanic to check.