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      11-08-2012, 07:07 AM   #1
Fed P
Private First Class

Drives: 135i
Join Date: Mar 2012
Location: Russia

iTrader: (0)

Car rough idle and stuttering - but only when cold

Hi everyone,

Recently my car has started to idle roughly and stutter for the first 1-5 minutes depending on how cold it is and how cold it is outside. Once it warms up, I can switch off the engine and turn it back on and it's smooth and there are absolutely no issues (at idle, driving or WOT).

I have changed all spark plugs and coils several months ago as a preventative measure as I bought this car second-hand about 7K miles ago and had no idea how old these parts were.

Any ideas on what this could be theoretically at least?

Injectors and HPFP are a possibility, but why would everything work perfectly once warm? I do not experience any long cranks even when cold by the way.

Carbon buildup is a possibility I would guess, but again it seems weird that the problem goes away once the car is warm.

Codes-wise I get misfiring on cylinder 4 and 6 (and once I had 5), and I also get the misfire on multiple cylinders code.

I took a look at my "new" plugs and they do very much look like this guys:
Having said that, I took a look at the plug from cylinder 1 (which reports no problems) and it too is blackened.

Does anyone have any other ideas or thoughts in general?