my monte carlo is idling high ? I changed the idle air control valve but did not help? What else could it be?

try changing throtle position sencer, and tempeture control sensor.

Yes, the PCM may not be detecting when the engine is warm enough to switch to "warm" operation, and if it's staying in closed loop mode, it's using a preprogrammed higher idle and fuel mixture to make the engine run. See if there are any stored check engine codes as well.

Papa's spot on here, blatantly the the throttle sensor.

I hope you did not replace any sensors right away,,,,try to reset the PCM and sensors...i.e. disconnect the negative battery terminal.... and pull all the wire connectors of TPS,IAC,COOlant SENSOR,and Knock sensor..and use contact cleaner and wipe it with clean ,dry cotton....put it back and connect the battery terminal...your PCM reads the default settings of its previuos run loop so, we just try to reset it ....see what happens.....

im having the same problem i changed everything deal with idle to the point where someone disconnected it so it would stop fluctuating to high. What seems to be my problem...

they did the reset on it too taking off the negative battery terminal and all that do u think its just a bad pcm?

if that did not work try a good check up on the coolant sensor. try to pull out the connector and place a 200 - 300 ohm resistor in the terminal as if we are insinuating a hot engine temperature.( the coolant sensor reads 200-300 ohm when the engine is hot or normal operating temperature). start the engine , the idling should be low. dont switch on airconditioning . try this one and see if PCM reads right.

Check the throttle position senser.