I replaced the motor in my Comanche with a matched one from a wagoner, both 4.0 sixes and were compatible. after the switch I had trouble with the donor having a fast idle after warmed up. I tried cleaning the iAC , vacuum , leak and the usual remedies I found on here. Cleaning with throttle clean with no real improvement, I started it up and watched it run, sure enough it started racing the idle up again. I gently tapped the butterfly closed a little and it idled down. I shut it off let it cool back down then with some 2000 grit sandpaper just polished a little on the butterfly close seat and the barrel of the throttle body enough just to clean it . has a decent idle since. Just sharing .....
Thanks,
Blaine
