QuestionMy 1992 Mit Eclipse 2L DOHC 5 spd has a second generation ISC motor. A few months ago, this problem arose: When engine cold (and ambient temp below, say, 70 degrees F), idle starts at about 12-1500 rpm, then slowly rised to about 2000 rpm, then oscillates between 1500 and 1800 rpm at about one cycle per second, until engine begins to warm up, then idle slows, albeit at an elevated speed of about 1000 rpm, but ISC then properly reacts to deceleration and loads. If I remove connection to Idle Position Switch DURING oscillation, oscillaton stops and engine idle normally (but at 1000 rpm)-however, engine performance if driving with IPS disconnected is less than ideal. (NOTE: Normally, the engine can be almost stalled out if IDLE ADJUSTMENT SCREW is closed, but now if it is screwed closed idle does not drop below 1000 rpm.) I've tested IPS and harness, and both OK. I've tested ISC motor warm, and it tests good. Haven't tested it cold. AFS tests good. Temp Sensor and harness test good. No Codes for any of the foregoing. SECOND PROBLEM: For a long time I've gotten a Code 11, OXYGEN SENSOR. O2 sensor replaced, harness and sensor test good, but still get code 11. Even Mit dealers, those few who will even look at it, can't tell me a fix. I am primarily concerned now about COLD IDLE SURGE. Any ideas?"
AnswerI think there are two o2 sensors on this, there is one before and after the cat.
As for the surge have you had the throttle body cleaned out and check to make sure that the injectors are firing the right amount of gas? Also Was this motor ever swapped out?
I would maybe check the MFI sensor because this will also give you idle problems. I had this problem with my 2.4l. Thanks let me know
