I have had this small issue when driving at full operating temperature with the a/c on. It only happens when I come to a complete stop. The idle will dip under 500rpms for just a moment and then raise back up. It seems that the engine idle does not change whether I have the a/c on or off. Aren't these trucks supposed to idle up about 100 or so more rpms with the a/c compressor kicked on? Truck in sig only has Magnaflow catback. Any help is appreciated.

 

Mine does the same thing.... but I didnt see you had only a exhaust..

Mine does that because of the cam I guess!

Good Luck To you

 

mine does that also, maybe due to the bosch 4's i've got in there right now. next couple of oil changes i think im goin to some diff plugs. i read somewhere on here that the bosch's will do that to idle.

 

btw, i put in the bosch's when i didn't know a damn thang about plugs.

 

Try cleaning your Throttle body.

 

If you have access to tuning, you might want raise your IAC valve values. You shouldn't have to unless you have a cam though.

 

The throttle body looks clean as new still. I have 25000 miles. I'm just guessing it has a sensor somewhere for when the a/c comes on. When I am sitting at idle, turning the a/c on doesn't move the rpms any.

 

yea mine does this too.

 

I have the exact same truck you do, 04, 5.3, and mine does the EXACT same thing you mentioned. I have a K&N FIPK, magnaflow catback and Nelson tuning. Sometimes it will idle down so low at a red light, I think its gonna die. Other than that, the truck runs like a raped ape, and has yet to actually die. Im kinda hesitant about taking it back to the dealer because I know they are gonna flash my comp. I know that Allen will redo my PCM free of charge, but I just dont want it to be down for 4 or so days.

 

I hear ya on the tune. Mine runs great also, this is the only problem yet. The idle dips low for just a second, but has never died. Seems like we must have a bad sensor or a small PCM tune problem. I will probably have it checked out at the dealer sometime before my warranty expires if I don't find out what it is.