its a 94, 1500, 4x4, 5.9L... when i start it in the mornings or after it sits for a few hours, it runs like crap. sounds like it has a vacuum leak, motor starts to miss!! runs like crap!! when it warms up everything is fine. i put a new TPS, and EGR valve in.. it was doing it b4 i straight piped it, so i know that aint the problem!! can anyone help me please?? could it be the idle air control??

 

Could be IAC is part of the problem. How is your plenum? Is it orginal? Is the gasket blown?

Pull upstream O2 sensor out and see if it runs better. If so, your cat is clogged, and indicates that plenum gasket is blown and clogged cat.

 

Did you install new o2's when you straight piped it?

And +1 on the IAC. Pull the TB and take the IAC off and clean both. While the TB is off, get a small mirror and flashlight, and look around inside the intake for oil. https://dodgeforum.com/forum/dodge-r...n-the-iac.html

 

I'd put my money on the upstream oxygen sensor, as the symptom you describe is perfectly consistent with it and the most common complaint indicating a bad one. Be sure your replacement is either Denso or NTK brand as the rest are way too likely to be completely out of spec right out of the box.

Idle Air Control valves tend to be more prone to act up when atmospheric humidity is high and/or the temperature is near or below freezing. I doubt it's your culprit.

 

"when it warms up everything is fine"

With a sketchy, heat-related misfiring problem like yours, you have to consider the (drumroll please ..........) crank sensor and cam sensor.

 

Betcha a dollar it's the upstream oxygen sensor.