Had the same problem.Replaced the IAC ,thought I fixed it.Next day drove about a mile shut my truck off.Tried starting it a few minutes later same thing won't idle.Took it to a friend,left it over night so he could check the engine cold(friend that works at a auto shop).It acted up for him ,he was able to hook it to a computer.All he said he did was clean the throttle plates.Run great ever since.Sounds silly but it worked for me.Hope this helps.
TheRodGod