Two days ago my car started to idle at 1500 rpm then yesterday it started to idle at 1500 then climb to 2000 then drop back down to 1500 again. It will do this from the time I start the car until I turn it off. I tried mesing with the idle adjustment screw and only managed to change the cycle from 1500-2000, to now 1000-1500. Who can tell me what is wrong.

 

clean out or replace iacv