1998 Daewoo Nubira Misfire/high idle speed

Hi Ryry,
I have the same year/model (although in Australia there is both a 1.6L and 2.0L variants - ours is the 2.0). Have been trying to fix a very similar problem, 1900 rpm idle, idle "hunting" (revving from 1000-2300 continuously), delayed throttle discharge, low power and erratic service light. Have had it in to 2 mechanics and 1 auto electician so far trying to fix. Found the service light related to faulty IAC code (not sure what the actual ODB code was). Replacing the IAC and resetting the ECU only fixed temporarily, after a couple of months problem gradually reoccured. Had it in again, this time they relaced the ECU wiring harness and reset ECU. Same thing, reoccurred gradually after about a month. Still don't know what the problem is but know what it isn't, so hope that is some help. Beyond that, the "experts" here admit they are stumped, if you have found the culprit would be great to hear about it.

Cheers

My car also has oscilating idle speed as follows:
when engine cold: 1000-2000rpm;
when engine warm: 1000-1500rpm.
It was checked : iac valve, sensors. The problem is from the car was new! Somebody told me about soft?
Did you solved your problem? Because sounds similar.
If yes, please advise me! Thank you in advance.