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Coolant temp sensor problems maybe?

98XJSport

Destiny is the rising sun
Location
Western Maine
I have a 98 XJ 4.0 Auto. In the past 2 weeks I first noticed my AC stopped working. Then, when sitting at the bank with the jeep running my temp guage jumped from normal around 210 to beyond 260 for a second and then back to normal and the check engine light came on. I took it from there to have it scanned, but the idiots lost the cable. The next day I turned the jeep on and the check engine light was gone. Then, a few days later I was sitting in it at idle and the temp guage dropped to below 100, and the check engine light came back on. Again, it turned back off within a day. I havent been able to be near anyplace to get it scanned while it is still on, and I dont want to be replacing sensor after sensor till I figure it out. Any suggestions? Thanks in advance, and yes I searched, the question is to broad.

EDIT: I also noticed that when at idle the electric fan would turn on every 30 secs for like 10 seconds.
 
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Clean the contacts of the sensor and plug with some kind of contact cleaner.
I had a similar issue with my 99 XJ. Cleaning the contacts took care of the problem.
Rinse with alcohol, let dry, apply some dielectric grease and connect the plug. This might very well fix the problem. If it doesn't, replace the temperature sensor, it can't be that expensive.

MAP
 
98XJSport said:
my temp guage jumped from normal around 210 to beyond 260 for a second and then back to normal and the check engine light came on.

A similar thing happened to me and my 1999. This past weekend, I was towing a light trailer up the Cajon Pass. It was hot out, around 102 I guess and I was taking it easy, windows down, just crusin in the slow lane, because I did not want to overheat. The windowns were down, A/C off, and the coolant temp was up around 220 (nornmal is just a tad below 210). I was wastching the temp gauge very carefully, and the just all of a sudden it jumped up to 260. I pulled over and shut her down as fast as I could. and let her cool down. Started her up again with the heater on and towed my traile rup the hill with the temp guage reading 220 with no other problems. I am guessing that it is dirty contacts since my tach and speedo and radio wiig out on me sometimes.
 
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