When I first start my 93' f-150 up it has an extremely high idle. After about 30 seconds it will calm down, but sometimes at stop lights it will idle high again. I have to smash the brake down to keep the truck from going anywhere. I cleaned the throttle body any it helped for a few weeks and then started again. Could it be the IAC, and where is that located on the 302 V8. Thanks

 

Try plugging the vacuum line to the brake booster first. You'll have to drive more conservatively since you won't have any assist, but the booster might be the cause of the high idle.

If it still idles up, use a stethoscope (3' garden hose) to listen around the idling engine for vacuum leaks. Concentrate on the intake, plenum, & all the vacuum lines.