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?