Temperature gauge is fluxuating 1994 grand cherokee v-8

SOURCE: driving me nuts

If it is automatic transmission with overdrive the lock-up torque converter is kicking in and out causing the rpm to fluctuate.Could be just the converter or maybe the overdrive going out.

SOURCE: Temp gauge goes to full hot while at Idle

Check the auxiliary cooling fan for operation. As the engine temp rises, it should kick on to bring the temp down. U may have a bad motor on the fan, or more likely a bad fan switch.

SOURCE: 1994 jeep cherokee linkage

Problem sounds like an internal pressure problem not a cable. If you are able to shift into all gears using the shifter, the linkage is being moved properly. It cannot "come out of gear" by way of the shifter.
In reality, if you were able to manually put the shift lever on the transmission into any particular gear without any shift cable at all attached, it would stay in that selected position forever till you got under there and moved it again. Depending upon what transmission you are using you may have a throttle cable running between the trans and throttle lever on the throttle body...this may have something to do with your problem but would also affect shift points. Any electronic shift controls are also suspect at this point. have it checked by a competent shop. In not being there myself, I can only offer my thoughts on what I would test going into the problem...after testing a better evaluation can be made. Good luck...Hope it's something simple.

SOURCE: my jeep grand cherokee started overheating at idle

try the water pump - first - make sure the radiator is really full - take the cap off cold and fill - if it looks full - start and run 8 minutes or so - then fill it up - look at ur fan belt - is it tight - tight is about how much pressure u use to make a firm hand shake with little movement - any movement over about an inch is loose - when the jeep warms up the belt can slip and not even make a noise - - new materials don't always squeal. - then be sure ur water pump is ok - they go slowing - the fins wear down - one more thing is the radiator - u don't say how many miles or what maintenance schedules you have or not so that's it for now

SOURCE: Ticking/Tapping when car starts but goes away???

I had what sounds like the exact same problem. It was an exhaust leak from the left (driver's) side exhaust manifold. This engine has a history of the manifold bolts breaking and causing the exhaust leak. The engine is also used on some Dodge vehicles. It sounds like a tick and I almost mistook it for a bad lifter. I took it to the local Jeep dealer who confirmed the exhaust leak. I replaced the left manifold completely and replaced bolts/gaskets on both sides (left/right) and it fixed the problem. Be careful, as the dealer tried to gouge me on the price. You are looking in the ball park of $600 parts/labor. I got parts for $120 and it took the better part of a work day to do the job.