Runs fine, but wont idle anymore

[rmusher]

Well, my buddy has a 92 Pontiac Lemans, 1.6l FI. We recently replaced the headgasket and the timing belt. Car would run fine, but wouldnt idle properly at first. Well, we brought it in my dad's garage, timed it (without removing any sensors) and than finally about 2 weeks later replaced the IAC motor. For about 5 days, the car ran great, but than, all of the sudden it wouldnt start unless you hold the gas down. It runs fine as long as you dont take your foot off the gas. The IAC is still working because I held my foot on the gas, turned the Defrost on, and after the compressor kicked on it corrected the idle properly. Tried to check resistance of coolant sensor, couldnt really get to it but upon removing the connectr while it was warm, it did change idle so Im assuming it is working to some extent. So far, have only checked this symptom while cold. Also, it idles fine just before the Idle set screw, if I press the linkage againjst the set screw, it tries to die. Heres my question, WHat do you think it is? Im thinking I need to retime it with the right procedure, because I know most insist on disconnecting a sensor. My question is also this, Why did it run fine for 5 days, now its crap? AGain, the temp has only changed from about an average about 43 degrees to about 30 degrees now, but I wouldnt think it should affect this. Checked for vacuum leaks, nothing so far. Cant really check fuel pressure because of TBI. HEre is recent repairs.

Headgasket and timing belt.
02 sensor, IAC motor and TBI injector.

[MagicRat]

Sometimes the IAC can be fried by excessive voltage or a voltage spike. Chances are the same problem that ruined the old IAC has also ruined the secong one. If you can get your hands on a factory service manual and a good digital mutimeter, you could at least diagnose the problem yourself.

[rmusher]

WEll, the only thing is, the first IAC, didnt relaly correct at all, viewing with the scan tool, the counts wouldnt really move, or were very sluggish. The new iac I havent had a chance to check with the scan tool, but seemed to perform alot better. Again, beforehand, the car would only run like crap with the AC compressor turning on (IE Defrost) and it woulndt compensate for it. The new IAC as I said, compensates for AC when I keep the car running. So, I can try to check for voltage spikes, but im not quite sure that is what it is. If anything ,ill bring the IAC up to school and we have an IAC motor tool. Any other ideas? the IAC passage looked pretty clogged and we couldnt really clean it well before, do you think maybe something got lodged in there and that is causing a problem now?