[frances9thone]

I had the same issue with rough idle at cold start, warm start and highway driving. But no codes for misfire or anything related to a miss. 2009 335i 3.0 coupe. I was convinced it had to be a vacuum leak based on how it performed. I found this forum suggesting spark plug gap at .035. I removed all 6 of the 3 pronged Bosch plugs which i had recently installed new and found the gap to be .010. Very close. Set the gap to .035 from the electrode and reinstalled. Held my breath and started the car....yes...problem solved. No more rough idle no stutter. Thanks Salzamani for your detail and all others who discussed this issue that led me to fix my car.

[stewbets]

Originally Posted by Salzamani

I also want to point out that spark plug number 1 is black on the tip where the electrode pin is. Black like carbon build up with a little bit of oil around the threads and the tip does smell a bit like gas. I had noticed this issue with spark plug number 1 even 6 months earlier which is why I decided to do the valve cover gasket 4 months ago. So why after the VC gasket change is this spark plug number 1 still turning black? Can anyone chime in with any theories?

Those symptoms make me think you have a leaking injector. At least that's what I experienced when mine was leaking. If I took my plug out shortly after shutting off the engine, I could even hear the injector hissing as it leaked.

[mosherif11]

Originally Posted by chris the man

Hi all, thank you for looking at this thread. Of the hundreds of threads I have scoured and bumped with a similar issue, we have had no luck.

My dads car, 2008 335i is having this issue.

Stumbling RPM's at cold start and at idle after being warmed up.

Recent services. less then 12k miles ago.
new spark plugs
oil change
new injectors
oil stand gasket
waterpump etc...

More then 12k miles ago.
new hpfp fuel pump

Cold Start. - Starts up instantly every time "no delay or lag in startup". On cold start it will stumble after a couple minutes between 500-800rpm. the car will feel shaky and feeling of misfires seem present

Warm Start. - Starts up instantly, yet at idle resting you can slightly feel shakes or misfires. Not as aggressive as cold start and it does not stumble as much. But slight misses feel present.

The car has been brought in 2 times last week. Injectors and Fuel pumps seemed to be just fine. Spark Plugs were changed just for precaution.

Has anyone else had this problem, been able to fix it, or experience anything like it? The car is never driven hard. Any help is much appreciated.

Any memory of what it was? I am going thru this as we speak!