GKRPL1

VIR997 I think you probably do have the answer! The symptoms you derscribe are EXACTLY like mine and the mechanics did mention lifters but deemed it unlikely. However pretty much everything else has been tried. The fault codes are always random misfires on 4,5 and 6. Like yourself various "fixes" have solved the problem for varying periods of time, a month, weeks, days and until the next start up. It is always perfect when warm so lifters will be the next job done - many thanks. I will keep everyone updated on progress. Loren and Paul Speed thanks for your comments too. The fuel and injectors seem fine and the fault codes are now stated. Thanks again everyone.

Hi Rich and thanks for that tip. I have looked at the earth wire and it seems fine, however an easy check remedy will be to add an additional one, even if only temporarily. It will at least rule that potential problem out. In case other people that have been kind enough to respond are following this I can now confirm that the air filter has been removed, cleaned and that I have run the vehicle in the garage without a filter in - same issue exactly. So thnaks for the tip but I can now state for certain that it's not air filter related.

Hi Paul and thanks for your rapid response. I replied yesterday but can't see my reply in the forum, so I am adding this one out of courtesy if nothing else. I really hope you are correct and appreciate the suggestion very much. It could well be something as simple as that and I will remove the filter and re-run the tests to confirm this either way. The filter is the genuine Porsche item and was replaced in a main dealer service only 3K ago. However, it is such a simple test I will do it as soon as the kids are back at school. Ironically it does highlight a gripe I have with Porsche and their "easier servicing" statements. Why the air filter box cant just have over centre clips like most other vehicles I do not know! So many screws, on the base of the housing, is just crazy in my opinion - just thought I'd mention that too. Thanks again for your help.

Thanks Brahimza, your problem sounds very much like mine. I am now sure it's not the coil packs as they are both new and swapped side to side on the engine, with the fault remaining on the same bank. The oil is genuine Mobil 1 and was changed between services as a precaution, together with the filter - just in case! I now hope, as the previous reply to my post hinted, that it could be an air filter issue. Once half term is over I will take the filter out for a day and re run the test cycle after cancelling the faults. Thanks for your ideas and your good wishes.

I really hope someone can help with this as I am now baffled. I have a 997 C4S Gen 1, 2006 model. I have had the vehicle from new and it has full OPSH. It is the 3rd new 911 I have owned so am quite used to them, the others were 996 C4S's. It is a coupe, 6 speed manual, Ceramic discs, UK spec right hand drive, all original equipment. The problem is as follows. The "check engine light" comes onto the display with a "visit workshop" message in the display. Once on the yellow engine symbol and red exclamation mark cannot be cancelled without a reset by Porsche. The issue is that the car runs perfectly, never missing a beat. The fault codes stored are intermittent missfire on cylinders 4,5 and 6. The display also showed O2 sensor swapped bank 1 pre cat, so.... First job was to swap the coil packs, which were tired and probably due for a change anyway. Fault codes reset and all was well, until the next cold morning. Start up was instant and perfect until the choke cut off when the revs dropped to slightly below normal tickover and then it started missing. Light comes back on. Stop the engine and restart it and it's perfect - but the ******* light is on again! Codes are misfire on 4, 5 and 6 again. Next was to replace the O2 sensor on that bank (carefully double checked by disconnecting the wiring plugs behind the tail lights, just to guarantee the convolutions of the exhaust didn't fool me as to which bank was 4, 5, and 6). Lights cancelled and all is well again - bear in mind the engine is still warm. Next cold morning - identical issue and light back on. Fault reads just the same. I now suspect faulty coil packs (even original Porsche parts could have issues) but rather than buy new I swapped 1, 2 and 3 onto 4, 5 and 6. Fault cancelled and home. Same problem next day - back to the garage and the fault is....... on 4, 5 and 6. The car has had a four year service at 20,000 miles and the plugs were changed, it's now done 23,000 miles, but I suspected that now it MUST be plugs. Since it's a low cost spare I swapped to 3 new in cylinders 4, 5 and 6. Light cancelled and all's well to go home. Next morning same issue. I now leave the car at the garage overnight, push it into the cold for an hour and then clear all the fault codes. I now start it with the KTS system plugged in. Fine untl the choke cuts off then intermittent missfire on 4 and 6. That was cancelled with the engine running, the engine note altered to a normal sweet running note and there are no recurring faults. The car was stopped, left to cool for 5 hours and the process repeated - exactly the same fault. So - with the diagnostics in place each plug was switched off from the box. Instant missfire on whichever plug was disabled. Next the same for all six injectors (which are bomb proof as far as I'm aware on 997's, especially at such a low mileage) and the effect is the same. Missfire the instant the fuel is cut. Now you see why I am baffled. There seems no leak on the manifolds. No air hisses and no scorch/suck marks are visible. In any case the fault only occurs as the choke cuts and only until the engine is restarted in "warm mode". It is such a narrow band and neithere cold nor hot - it runs fine at both temerature extremes. Has anyone heard of a software fault? Has anyone experienced anything similar? All help gratefully received, whilst the car runs fine the dash light is driving me mad. Many thanks in advance.