My '06 C2 w/23,000 miles, CPO warranty, has been running great all spring & summer since installing FabSpeed 200 cell cats & Softronic re-flash (2000 miles). Always burn Shell 93. It sits most of the week waiting for the weekend. On Friday, it threw the following codes: P0300 with P0301, 302, 304, 306. In reading all the previous posts; MAF, coils, spark plugs have been suggested to be replaced, but on considerably higher milage cars. I read about contaminated fuel, but my local Shell station sells plenty of fuel at this location, but I guess still a possibility. I assume I can clear the codes, but there there still an issue with the car.
Presumably I'll get it down to Porsche on Monday. Do I re-flash it back to stock? Could Softronic have anything to do with it? Any thoughts out there?

 

Since you had put several thousand miles on it I wouldn't think the flash is the cause of the problem. We haven't had misfire issues with this file. The software doesn't change and is the same as the day you installed it. The stock software can and will at times for the same reason listed next cause the same faults. The problem may be the fuel, spark plugs, Coil packs or 200 cell cats. Gas does get contaminated regardless of how much gas they sell etc. The spark plugs should have been replaced twice by the age and or mileage by now. The coil packs tend to crack with age and the cats can come apart causing misfires.

The P300 is a general misfire that is thrown when any cylinder has a misfire. The 301 is specific to cyl 1 and 302 to cyl 2 and so on.

You may want to clear the codes and run out the gas and then get some fresh from another station. Check if you then get more misfires and if so replace the plugs if they have not been and check the coil packs at the same time.

 

Thanks for the response. The FabSpeed cat are new (< 2 months & 2000 Miles); it ran perfectly last weekend, filled a half tank, sat for 4 days then got the rough ideling, flashing CEL, and then 5 codes. Cancelled the codes, re-started the car, it threw the codes right away. The car is still under warranty, I'll get it to the dealer tomorrow. I was hoping for a concensus on the possible cause.

 

Please let us know what ended up causing the misfires, my guess would be spark plugs or coil packs.

 

when you get massive misfires on all cylinders - MAF is the first to be suspected.
take it out (carefully) and wash in MAF cleaner - get it from autozone. do not use any other cleaner - get a can with 'maf cleaner' clearly written on it, and use whole can spraying from all angles.

after maf next one is coil pack, next are spark plugs.

 

P dealer tells me the (L or R?) coil is rusted fubar. The other one is next. Okay, both replaced under under CPO warranty. Going to do the spark plugs at the same time. Althought this car spent it's first 4 yrs & 17K miles in S. Illinois, should the coils have deteriated that much? I have never replaced a coil in any car at at any mileage. I'm not *****ing per say, but is it normal for P car coils only to last last 4 yrs/ 17K miles?