Here's a little bit about my Xj:
99 4.0 automatic with about 197xxx miles.
About 6 months Ago I replaced my crank position sensor and IAC.
Living here In miami we go through a lot of water and mud when we go wheeling so keep that in mind. I'm not sure the lifespan on sensors but here's what happened.
Went wheeling over the weekend, broke my front end spider gears. Found a replacement dif so I swapped it out completely. Jeep drove great. Engine bay was full of sand so I pressured cleaned the engine bay and I guess I messed up. I took out the distributor cap, ignition coil, wires, iac. Tps and cleaned them all and put dialectic grease. When I turn the jeep on, the rpms climb to 3,500 for a few seconds drops then stalls. If I put it in drive it's fine then stalls. Could it just be a coincidence that I washed it and now my CPS is bad again????

Sorry for the length but wanted to explain everything

 

If you have a multi-meter, check all of your sensors. They hate water and mud. I'd start with the TPS then maybe the IAC. If it fires, it might or might not be the CPS. Was it OEM or parts store brand? Lots of folks have had bad right out of the box CPS's from parts stores. Most people recommend only dealer sensors for this reason.

 

+1
Who would have thought to make a 4X4 water resistant?
With the exception of the terminal ends of spark plug wires, it's not a good idea to slather everything with dielectric grease.

 

Just an update. Swapped out the CPS and it started better but the revs were still high. I disconnect the IAC and it ran fine. Went to local parts store and replaced the IAC and the TPS and it runs and idles perfect!

 

Good on ye, mate!
Did you check in between swapping the IAC and the TPS? Just to see which one was the bad boy that didnt take the water too well (my guess,the TPS).

 

Agreed dielectric grease is a great thing "When used in moderation" but too much can be just as bad at times.