Need Help: Rough Start/Idle when Cold

[GopherBrain]

I need r3vlimited help. My mechanic (good, but not an e30 guy) can't figure this out.

My car has had a few months of rough starting and idling when the engine is cold. It turns over fine, but doesn't even try to catch for 10-15 seconds each morning. Then, when I drive to work it shakes when I am idling at a stoplight. Recently, I have had trouble taking off when the light changes, the car loses power for a few seconds and acts like it will die.

This does not happen when the car is warmed up, it runs smooth and starts easily.

The car has relatively new OEM plugs. My mechanic looked everything over, replaced the coolant temperature sensor, and tested the fuel pressure system, and everything checked out, but my car continues to do this. WTF?

Thanks for any help.

[jlevie]

That sort of problem makes me think of intake leaks. A cold engine needs a richer mixture and even a small intake leak can cause a rough idle. Until the engine warms up the DME runs in open-loop mode, so it can't compensate (based on data from the O2 sensor) for un-metered air.