slicky rick

No cel, change gas, new engine mounts, no cracks with the coils, spark plugs looked good, 26k kms, no faults on piwis. The misfire seems there even when throttle is applied up to 2500rpm with car in park or nueteal. Engine does not consume oil. This slight misfire like vibration is only felt when idling and car not moving when throttle applied. When the car is moving, there is no evidence of this vibration, accelerates well and generally good running. What could this be?

neanicu

Vacuum leak. They manifest most at idle.

mdrums

Rick you should go get a new car...through your posts you sure do have a lot of problems. Good luck

slicky rick

thanks mike but still enjoying her. maybe i will upgrade to a ferrari 458 one day but for now my 997.2 serves me well as my Guinea pig and the small problems add to my knowledge of cars and how to make them perfect. REmoves the fear of having better and more expensive cars. you should have seen what i went through with my 1988 mb 190d which i got brand new…that was exciting and i still have her and she still runs like new after 270k km. My driver says she is the best amongst all my other cars, which i agree. when i get things right i feel satisfied. dont you? nevertheless, maybe you have an idea with the cause of the miss

mdrums

I like perfect or as perfect as possible. I have had 4 997's and only 1 issue...my 2009 had a header weld develop a crack...so the dealer replaced it. Plus I track my cars so they are not babied but well taken care of.
I had a BMW x5 with lots of electrical issues but since then many vehicles with zero issues.

I'd love to have a 458 too...but I really like the drivability and daily use if I chose of Porsche.

user 72902

Here is a decent tech article from Pelican Parts for tracking down a vacuum leak. I think that was a good suggestion.

http://www.pelicanparts.com/techarti...cuum_Leaks.htm

Macster

Your imagination?

Sorry, cheap shot.

If there is no load if there is no vehicle movement the VarioCam Plus system can perhaps be left in low lift mode to reduce pollution.

I note you note the behavior is not present when the vehicle is moving.

Absent any issues when moving, absent a CEL and any error codes, I'd say there's no problem. You can certainly run the behavior by your trusted tech and get his input.

Oh, one other point. In the past with other cars when changing motor mounts if this is not done right the mounts can be under some odd tension or twisting situation which can change the engine vibration harmonics. I had one motor mount under such tension -- before I realized what I had done -- that rubber material separated from the mount plate -- IOWs the mount failed prematurely. When this happened and as I was removing the failed mount it occurred to me what I had done and when I installed the new one I lifted the engine up (big old cast iron V8) and installed the mount then lowered the engine. This resulted in the mounts being under less strain, no strain really. They were under almost pure compression with the engine not running and they lasted until I sold the vehicle years and thousands of miles later.

slicky rick

thats ok mac, i was expecting you wuld come to the rescue...however, motor mounts were replaced by the dealer. Not my imagination because we compared it with other cars in the service area and mine indeed had a bit more vibration that the others. it was the after sales guy of the dealership who ordered the throttle body cleaned and the iginition coils and spark plugs checked. All turned out ok. so it exist no doubt but it might be like the oil consumtion thing that there are cars that have oil consumption and other that do not yet all are still normal.... if i cant find the cure....i will say its better than oil consumption.

slicky rick

jk i will try out the vacuum leak check maybe just maybe there could be a slight leak somewhere....somewhere i hope easy to find.

miketporsche

I was wondering if you ever tracked down your problem? I have a similar situation. Slight misfire on cylinder 6 ( as measured by dura metric cyl misfire counter). No cel.

slicky rick

Havent, really. The dealer cleaned onut the injectors. Holes were clean but there was a dusturbing amount of build up around the injector. Something "crusty". Ultrasonic cleaner and all new gaskets and rubber rings evertyhing was back. I noticed a bit of driveability improvement. Not really sure if it was due to pdk software upgrade with corresponding torque adaptation or it was the injector being cleaned that gave the car somewhat more torque. But i am now trying to investigate carbon deposits as a possible source of the lumpy idle issue. Mac, the car is really awesome when running. No running issues whatsoever. Not even a single oil drop consumed in my 1 year maintenace period and not even a decrease in coolant amount during the same amount of time. You may be right.. Normal op but not normal compared to other os the same kind....997.2 3.8 dfi by the way.

slicky rick

By the way the lumpiness at constant 2000 to 2500 rpm did go away after what has been done so far. Been reading a bit and it seems that although carbon buildup might be a case for dfi engines in general due to the inherent nature of the design, cleaning the buildup behind the valves should not really be that hard and expensive. Walnut shell blasting seems to be a good solution and simply involves removing the intake manifold which should be easy.

millertimefl

rick does your idle bounce around? Is it happening only first 15 minutes or so after cold start?
My 2010 C4S idles poorly and the tach jumps around +/- 200 RPMs ONLY before my oil temp gets around 200. If car is warm at all or even at lunch time after sitting for 4 hours it idles perfectly. All high revs are smooth. I cleaned the MAF but no difference. I am thinking vacuum leak.
I have an appointment with dealer next week...

slicky rick

not really much movement on the tach needle brother. its just you feel a bit of lumpiness through the seats. At least yours idles perfectly after a the cold start. lets keep everyone informed on what progress you and i have to share reagrding the idle.

alexb76

WHY did you have change your engine mounts for such a young car?