I've got a 89 XJ with 4.0 and manual tranny and am having problems with high idle.

Revs to 2000 rpm when started then drops to 900-1000rpm and when it warms up rises to 1200 rpm.

Here's what I've checked.


TPS cleaned and set voltage to .08
CPS tested when hot - 242 Ohms between A and B wires
Latch relay test term. 87a to 30 = continuity ; 85 to 86 = 79.9 ohms
PCV and CCV look ok
Checked for vaccum leaks with a propane bottle and found none
Cleaned ISM motor
Unplugged ISM motor and started engine - revs to 3500rpm

Wiggled and shook everything and seems to be ok, no loose connections.

I say it's a vacuum leak. Check in your charcoal cannister lines, the tcase lines, axle, etc. Wherever you wouldn't expect it, obviously.

Bryan

Check the vacuum line to the power booster.

A leak in the intake manifold gasket will also cause a high idle.

Originally posted by DE Jeeper
A leak in the intake manifold gasket will also cause a high idle.

I figured that's where he checked when he said he checked with the propane bottle. :D

I don't think it a vacuum leak. I went over the whole engine with a propane bottle and no increase in rpm. I checked vacuum lines at the tcase and my old axle vacuum lines are plugged. I seem to think it's in the fuel system electronics, but may be wrong. I find it strange that the rpm's change a little as the car warms up.