had engine light say that my 97 lude is running rich.the car also has an idle fluctuation mostly when transitioning from cold start to engine full warmed up. have already replaced map and o2 sensors and tested iacvalve and the warmup mechanizm on the bottomside of the throtlebody.and the idle air screw on the throtle body dosnt seem to make any difference in idle speed.it always goes back to 700 rpm wich is where it should be but why dosnt the screw seem to work?

 

Is there any buzzing noise from the screw?? Also is this an OBD2 conversion? Grab some carb cleaner and look for gasket leaks around bypass and throttle body area, I had a similar problem and that was my solution. If your running rich I would first think that it had to do with your O2 sensor but since you've already replaced it, it must be dumping in fuel for another reason, were there any other codes on your CEL?

 

i will check that out now but there arent any buzzin noises.my car came with obd2 stock after 96.no other codes that havent been addressed.thanks for the info.

 

It'll probably pay to pick up some carb cleaner and cheak for Intake manifold leaks. keep it posted I'm curious as to what the problem is.