car runs rough until warm, sputters, when warm it is fine.

[clydesdale]

The car is an 87 325is . The cold weather has reached the north east and my car runs like crap for the first 5 minutes. It sputters as if I burned a plug wire. When it is warm it is then fine. THe only thing that I had noticed was that about 2 months ago the car had a knock or predetonation sound when I really got on it. But it only did it for a second and although very mildly annoying, it did not concern me greatly. It was only for a second. I have about 38k on the current tune up parts. I replaced the o2 sensor about 2k ago. Thanks

[jlevie]

A rough cold idle that smooths out once warm on this car could be a bad DME engine temp sensor or more commonly an intake leak. A cold engine needs a richer mixture and even a very small intake leak can cause a cold running problem that dissapears once the engine is hot.

[Ray McCooney]

The car is an 87 325is . The cold weather has reached the north east and my car runs like crap for the first 5 minutes. It sputters as if I burned a plug wire. When it is warm it is then fine. THe only thing that I had noticed was that about 2 months ago the car had a knock or predetonation sound when I really got on it. But it only did it for a second and although very mildly annoying, it did not concern me greatly. It was only for a second. I have about 38k on the current tune up parts. I replaced the o2 sensor about 2k ago. Thanks

Any increase in the car's coolant consumption?

[TwoJ's]

I also think that a coolant temp sensor may be your problem.

[clydesdale]

The car continued to run like crap today, even after being on for 45 minutes. My last full tune up was 37k ago. This only kicked in when the weather got really cold. The coolant temp sensor is cheap though. Any further thoughts.

[clydesdale]

It was a broken insulator on one of the spark plugs. It was diagnosed by removing each spark plug wire while car was running to determine which cylinder was not firing.