hmm osunds like it needs to warm up, liek the old carbed engines b4 it starts to idle nicely, im no mechanic but mayeb your thrmostat is broken and your cooling th engine down b4 it gets up to operating temp??
the temp gauge could be working correctly and the thermostat not working, they're two different sytems, when you turn your engine on, does the gauge slowly rise over a course of a few minutes or does it sit at c for a minute then suddenly jump up?
I have the 4.0 and have the same type of problem. Mine kinda stutters but it's barely enough to see it in the tach. You can't tell it at all when you are driving, just sitting still. I thought it was the plugs so I changed them out and it didn't change it one bit. Don't know what else to try.
Mine does the same thing after I start it. The idle will initially peak and then drop, shutter a little and then level off. It has never stalled so it's on my to-do.
I'm thinking it's related to the MAF sensor or idle air control valve. I have a '90 Brono that is notorious for this only it's much worse. I literally have to hose out the MAF sensor with carb cleaner 3-4 times a year.
I'm still ramping up on my Jeep as far as the details for the engine control systems. I "assume" it has a similar system with a MAF sensor and IAC valve.
hmmmm now that i think of it do jeeps have ecm's? cause that could be it too. but i just bought the jeep and it could use a tune up and a new serpentine belt. and i plan on changing the oil this week also so ill pick up a chiltons book and start working so ill let ya know how it goes.
A PCV valve may run $8... The Ignition Control Module (ICM)...aka "the computer" is a whole lot more ~ $500.
The carb. cleaner is used to clean the throttle body assembly (the aluminum component located on top of the engine that mixes fresh air into the engine).
You will need to remove the fresh air supply duct (plastic snorkel) then you can spray the cleaner into the engine while it's running. Be careful - wear goggles and only spray a little at a time around the inside of the bore. The engine will run a little rough till it clears.