Hi, I have a 1995 Mustang with 3.8 v6 automatic that will idle rough when cold then when warm idle somewhat okay. Motor slows revs and runs rough then smooths back out only to go through another cycle or two of this. Changed out egr sensor and plug wires, still no luck. Engine code came up as lean condition. (Two seperate codes but very vague)
Perhaps it might be a bad idle control valve, distributor shaft, or ECM. Sometimes when the ECM is damaged or not working correctly your car may have hard to trace problems (like engine timing issues) or show false " check engine" alerts. My 1991 Mustang GT has this problem (bad ECM) and it has been a total headache to trace it to the ECM. The bad ECM has caused my car to have idling issues when the engine is started hot or cold. However, after allowing my car idle for 2 minutes or 2 minutes and 40 seconds my car's idling issue corrects itself.
November, 10, 2007 AT 7:06 AM
If it's a cold start issue, try changing the ECT(electronic coolant temp sensor) It's right behind the coil.