I'm just gonna copy this from my bimmerforums thread.
I was getting a maf code and the car is running extremely rough, idling at around 400, HAS NO POWER, even if i put the pedal to the floor and hold it there it takes a very long time to get to speed, it even sounds weird like its not firing on all cylinders, like a puttering sound.
It started out of nowhere, at a stop the idle dropped and started running really rough, continued to drive and the CEL came on and lost power and started sounding weird. It has been having an on and off issue with a rough and erratic idle, sometimes even stalling, for the last month at least but always drove fine.
I replaced the maf from one I got in the junk yard and it did not change at all! So now I'm pissed I spent $40 on a maf that either doesn't work or isn't the problem and I cant return it at all.
If I unplug the maf and drive it is the same thing, if I unplug the ICV the idle goes up put there is still NO POWER and running rough.
What else could the maf code be??!!!?!!
In the last week I have done some work to it I changed the spark plugs to bosch iridium fusions, got my electric fan installed and seafoamed it. Could any of that be causing my problems?! I was thinking a spark plug failed on me but wouldn't it give me a different code?!!
Its still giving the maf code even with the new(used) maf.....
fuel filter has less than 3000 miles on it, swapped fuel pumps with my other one, all new intake seals and manifold seals with sealent on them trying to fix the stalling and idle problem from before. intake boot is fine.
So I spent all day in the on and off rain taking off the intake manifold, put a new pcv plate on, resealed all the gaskets and rings, double checked the intake boot and everything, theres no way I have an intake leak now. Started it up it was fine check engine light was on for a second then went away, it was idling good, had good power, everything was good right? Well as soon as the temp got near half way it started running like crap again, no power, low and rough idle, and sounds weird under acceleration. This has to be some kind of sensor issue and not a intake leak. Could it be those water temp sensors on the back? Or what could it be otherwise cause I just don't know anymore.
HELP SOMEONE PLEASE!