Just wanted to share my 2 cents on this topic, I know the last post is from 2015 but I hope this helps someone else.

Car in question: 2003 330Ci @ approx. 168K miles.


  • I do not think it is the battery or alternator, my wife's car has been experiencing the same issue for literally the last 3 or so years, basically the whole time we owned it. About 4 months ago, I also had the battery and alternator replaced and the problem continues to persist even after.
  • Valve cover gasket was replaced and inspected to confirm no oil leakage into the cylinders.
  • Fuel Tank Breather Valve replaced with new OEM to no avail. (Purge Valve)
  • I had swapped an ignition coil on the affected rough idling cylinder but the code had not come back since to scan and see if code follows. I'd also like to point out that for this particular car it did not take days of sitting to cause rough idle, but even cold weather would intermittently cause it.

Possible unexplored culprits:


  • CCV, the car currently has a nasty oil leak and I'm almost certain that's where it hails from. (Stock CCV @ 168K)
  • Fuel filter... unknown if OEM or replaced prior to our ownership.
  • Injectors as previously mentioned.

I've run out of patience with this car and now that we have a 3rd vehicle, I'm in the process of trying to talk her into an E92, E82, or M3 SMG.