Bmw Serie 3 F30 THAT have idling problems

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.

chris the man
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I think i have a similar problem. Here’s what’s been happening.

70K miles): Car begins misfiring intermittently when cruising at highway speeds (80ish, i cruise fast). Frequency of misfires increase until the engine starts shutting down cylinders. Would happen once in a 40 mile trip, within the last 10 miles. I’d pull over and restart car, and drive away with no problems. Went on for about 2 weeks, progressing to 2 or 3 restarts per trip. then wouldn’t run at all without misfiring. Took it to an indy shop cause i thought it was something severe, and realized spark plugs and coils were never changed. Indy shop changed bank 1 coils and problem went away. for 2 days. Ran worse than before, so i changed bank 2 coils and all 6 plugs at the same time. I noticed some oil in the spark plug well (on top of plug by coil boot) in cyl 3, and slightly heavier in cyl 4. both cyl 3 and 4 were dark and wet when i pulled them out.

after 2 weeks, ran without having to restart. but now i had intermittent misfiring at idle when cold or hot.

August: Misfiring to the point of having to restart again in last 10 miles of my 40 mile commute. but only on REALLY humid days. also rough start on humid days. dry days, no problem starting/shutting down cylinders. but had idle issues.

76k miles): I noticed a slight rattle in the engine bay starting back in Jan/Feb timeframe, but it was slight and i never did anything about it. It progressed to the point where i thought it was wastegate rattle so i took the car in to the dealership to take advantage of the turbo warranty. turns out there was something in my exhaust stuck between the cats and resonators. didnt pay the 400 for them to evaluate further (125 was enough). Dealer also told me the valve cover gasket was leaking and needed to be replaced. 2 weeks later, disconnected exhaust line at the flanges after post-cat O2 sensors and turned the whole exhaust up on end. dumped about a full CUP of mostly black/carbon colored metal chards/powder and some small honeycomb chunks.

No more rattle, and misfiring COMPLETELY gone (at speed and idle) for 2 weeks. thought i had fixed the problem.

84K miles): 40 mi trip means restarting 2/3 times on average. Cold starts are HORRIBLE for the first 2-5 minutes. stumbling idle, where if not gassing it, it’ll shut off. and when first starting, a loud whistling sound with VERY reduced power. with power returning instantly and dramatically as soon as the whistling stops (within 1st minute). And an occasional quick metallic screech (1 sec or less) on a cold start. Warm days, and only the misfiring to deal with. no loss of power, no metallic sounds. simple restart is all it takes after 2-3 minutes of driving. I pulled the engine cover and the trough where the spark plug wells/injectors lie is FULL of oil. on a breezy day, can see the occasional waft of a white smoke come over the hood from around the front passenger wheel well. only getting 22 mpg avg hwy now, used to get 27-29. i can smell fuel when idling.

Finally bought a BT cable and pulled codes for misfiring and post catalyst fuel trim system too lean on bank 1. also bought the Haynes manual. Seems like the leaking VCG can impact a lot.

I realize I’ve let things go to the point where I probably have a couple problems that need to be fixed. the symptoms aren’t helping with the troubleshooting. Misfiring at idle, misfiring at speed, fuel trim reading lean but running rich, leaking VCG.

1) VCG needs to be replaced immediately (just arrived). Probably contributing to idle issues. also, the oil leaking into the spark plug wells could be shorting out/impacting ignition.

2) Oil is most likely running onto the other sensors below. so need to start looking at them all when i replace the VCG. VANOS Solenoids, Eccentric Sensor, Cam Position Sensor, Knock Sensors, etc.

3) Need to look into new coils/plugs based on what i see (haven’t pulled those)

4) Need to look into replacing injectors (based on condition of plugs). condition).

PLEASE HELP. i just want my car back. living the misery, reminiscing of the good times!

02-15-2015, 10:50 PM #2