Ever since i replaced my 5.8 a year ago, my truck is either trying to push me through an intersection at stop light or its dying at idle. Ive had 2 shops look at it and both cleaned out the idle air control and one fix a couple of vacuum leaks. Its still is doing the same thing. I dont know which shop did it, but i found the idle adjustment screw had been backed all way which might be why its dying sometimes. Also if i make a trip to town its idling high when i park, when im leaving and start my truck my idle is low and dies after i put it in gear if i dont hit the accelerator quick enough. By the time i get to the next stoplight, its trying to push me through it again. Sometimes when its trying to push me through the stop light, i can put it in neutral while at the stoplight and it revs about 500rpms higher for a half sec then down to what feels normal. Its a hit and miss. The next stop light it might be idling high or feels normal or trying to go dead.

I wish the shops around here would just quit saying they have an "expert" on idle air engines.

Thanks

 

The throttle stop is not an idle adjustment screw. It is typically adjusted so that the throttle blades don't stick in the bore while closed or barely a turn past that stick point. The ecu reads tps on initial power up to see if its in "idle range" and then adjusts iac to adjust for it. If the throttle stop is holding the tb open too much then the iac usually causes high idle.

Few things to check
Is the brake booster leaking vacuum when at high idle
Is the PCV valve stuck open
Do you have an intake leak anywhere. Check by spraying carb cleaner or brake clean or starting fluid on all the gaskets.
Check to make sure tb isn't held open too much (too much air and ecu doesn't give enough fuel)
Check tps adjustment. .9-1 ohm I believe.