By the book, it says that "normal idle speed is 850 rpm, but there is a lot of factors that will bump it up a little or keep it lower. Such as altitude, mileage on the engine, last tune up, and a multitude of others.
I don't really concern myself if its between 750-1000 rpm.
'87 YJ, 4.2L built and bored, 8.5" of lift, 8.8 rear, AX15/NP 231, Tom Woods drive shafts, Flat fenders, 12,000LB winch, Custom bumpers, Rattle can paint job. Never completed...
No codes, other then the usual 12,33,55. I also noticed tonight that coming out of the vent on the valve cover where there's normally a PCV valve Im getting oil going into the air box.. Not sure if that's normal? Also when I go to stop and take the jeep out of gear (5 speed) it hangs at like 1200 rpm and then will suddenly drop to under 500 rpm and then level back out to about 500.
Mine idled low when I first got it. Around 500 rpm or so. I changed the TB to a 4.0 TB, reinstalled the 2.5 IAC housing & put on a new TPS. Now it idles around 700-750.
Since you say it hangs around 1200 when you pull it out of gear, it almost sounds like the TPS is on it's way out.
The oil in the air box is blow by. I've said it before, AMC motors are filthy motors. My first 95 had blow by when I took ownership of it at less than 2 years old. Some blow by is normal, if it's literally puking oil in the air box enough that the TB is filthy & your rig is smoking because of it, the rings are shot. Clean the CCV ( what would normally be a PCV) real good. Make sure nothing is blocking the line. They're notorious for clogging up with sludge.