My '94 Jeep V8 (80 000 miles) somtimes fail to idle. It just stops
when i lift of the gas, usually while driving at slow speed but it has
also occured at moderate speeds. The engine starts again witout
hesitation and after a few minutes driving the problem just goes away.
There doesen't seem to be any pattern to it. Is there some kind of
solenoid or other electronic gizmo that engages som kind of idle
"mode"? Might this just be a loose connection somewhere in the idle
control system?

Another problem is a slight vibration that occurs at about 60mph. It's
doesn't seem to have anything to do with the engine since shifting
into neutral while driving doesn't change the vibration. Also it only
occurs while running under very light engine load. (almost on the
verge of coasting) If i accelerate it stops, and it also stops if i
lift off the gas completely. This indicates that its not any wheel
imbalance either. Could this indicate a problem in on of the diffs? Or
can it be a imbalance in an axle or worn CV joints? Theres also a
slight whine from the drivetrain but i'm unsure where this comes from
- after all there is a lot of gears down there (two diffs, reduction
gear etc.)

Any ideas anybody?