For the longest time my truck had idled kinda rough and a little high. It always had stutters in the idle. I finally decided to do something about it and I replaced the IAC. It idles smooth now and a lot lower rpm, but my problem is at startup it sometimes hesitates and will sometimes die. If I have the ac on full blast it always dies.

Is it just that the idle is too low? Not pulling in enough air? I have an XL so no rpm gauge so I go off sound.

 

I'm not sure where to point you right off. IMHO it could be the ac compressor bogging down the engine which is now running at lower rpm's. Does it do it with the hvac system off? If so then maybe your tps was adjusted to try and compensate for the IAC giving fast idle and it needs to be readjusted (replaced?). I would start by using a multimeter to test the TPS for proper volatage, unhook the serp belt and spin the idler and tension pulleys by hand to ensure smooth and easy movement. It could also be that the alt isn't putting out enough power in idle and the battery doesn't have the juice to keep her running, this can be checked (usually for free) at any auto parts store. Try pulling codes to see if they can lead you anywhere.