My 99 dodge ram 1500 4x4 with 5.2 v8 gas burner runs fine but when I disengage the clutch to stop the truck dies it always cranks right back up. I have put 2 new IAC on it I'm no mechanic so i really could use some help figuring out what the problem is also the cat. is gone so the o2 sensor is just hanging I get about 8 mpg on a good day
Also I tried to adjust the idle ,checked plugs ,plug wires cleaned the tps and nothing has helped

 

Idle isn't adjustable...... Its controlled by the PCM, via the IAC. If you haven't yet, reset the PCM. Disconnect battery, turn on headlights for a few seconds, turn off headlights, reconnect battery, turn ignition to "On" (not Start), count to ten, THEN start the engine. PCM should figger out idle pretty quick. One problem you may run into though, these trucks just don't like aftermarket sensors in critical locations. IAC is one of them..... May need to spring for a genuine Mopar IAC.

You can get a weld-in bung for the front O2 sensor. That'll help with gas mileage.