Well I had a really rough Idle, ran decent when in gear driving. I replaced the IACV stepper motor (with a grand cherokee one) and now my idle sits pretty smoothly around 750rpm (seems kinda low to me). Also, when I put it in drive and I dont touch the gas it will accelerate on its own, in a two hundred yard stretch I was doing about 20mph. Any idea what could cause this? I also noticed at idle it puffs a little bit of grey smoke.I cant really atest to whether or not it did this before because I recently got the vehicle so I dont know.Any help would be greatly appreciated...Btw, it is a 96 D1 4.0 with 155k miles, 5kmiles/1 year since full head job on the engine.thanks,spencer[/align]

750RPM is on the high side, 500-750 is normal for a DI.
Clean the throttle body, your butterfly valve may be sticking open and that is why you gain speed at idle and in gear.
As for the grey smoke, sounds like you might be running rich.

alright well I guess I am fine then. It teeters in between 500-750, usually around 750.


What can I do to lean out the mixture? Is it all controlled by the ECM or what. I will spray the throttle body and linkage down with carb cleaner

Yes the idle is controlled by the ECU, you may be having your trouble because you installed the wrong IAC and it is sending the wrong signal to the ECU.
How much was the Jeep IAC?

It is only $42 from AutoZone and I reallydont think that is the problem. I have read from multiple people who did this on other Land Rover forumsand none of them have had any problems, my rover definately idles much better with the new one its just not great yet. They are supposed to be EXACTLY the same except for the angle the plug attaches which is not a problem.


any other ideas?


Thanks,
Spencer

What was your idle doing before you replaced the stepper motor?