I have heard that the FITV(sp) controls the cars rpms when the car is cold and that the IACV controls the cars rpms whent he cars is warm but i have also heard that the FITV controls both warm and cold. Which one really controls the cars RPMs when the car is warm. Need to figure out which one i need to replace so that my car will idle right because right now the RPMs just jump irractically from 900 to 1500 RPMs after the car is warm. Thanks in advance

 

The IACV controls the idle when the engine's warm.

The FITV is supposed to raise the idle when the engine's cold. It doesn't really 'control', but it just lets extra air get past the throttle. When the engine's warmed up, the FITV is supposed to be completely closed. So it's not supposed to have anything to do with idle control after the engine's warm.

One way for the FITV to screw up, is that it doesn't close all the way when it's warm. So it messes up your warmed-up idle control.

 

The FITV becomes useless when the car is warm. It should allow NO air past it when the engine is at operating temp.

With the engine hot, and the intake tube removed, unplug the IACV - is there air being sucked through either hole?