jrmboat

My first post and I already need some help. I just put a 4.8 and 4L60E into my Jeep YJ. The motor is out of a 2001 Silverado with 89K miles. Computer is stock except to have egr, rear O2's, vats, etc. removed. Fired it up for the first time and after a few minutes the idle speed starts to flucuate a few hundred rpm. If I hold the rpm at about 2000 and then let off the gas it tries to stall. When I drive it, it seems fine except for when I come to a stop, the rpm drops and it sometimes stalls. Checked for vacuum leaks and I think there are none. No check engine light but I have not checked for codes with a scanner. Not sure where to go from here. Any help would be appreciated.

rotor vs. piston

iTrader: (3)

Sounds like vacuum leak(s) or a bad MAF. Try unplugging your MAF and see if it levels out.

Docked Wage

Sounds like you have an unmetered air issue ie bad MAF or vacuum leaks like RvP said above.

If not it's just a guess but the IAC (Idle Air Control) could be stuck or sticking and not throwing codes.