I have a 2001 Cherokee sport with the 4.0L bone stock except a lower radiator hose heater.
I live in anchorage AK and its been in the 9-15 °F range outside so i usually start it and let it run for 5-10 minutes before i leave.
After i had almost driven 10-15 miles on the highway to work i noticed the temp gauge was reading way lower than normal, conveniently, i had my cheap OBD2 scanner in the back seat so i plugged it in to see what the computer was getting and it was reading ~ 138-143 °F

Then suddenly while im looking at the gauge when i got back from work and it jumps to 190 for a bit and then right back down to 140... Does that mean my temp sensor is bad or the gauge?



Normally it operates right around 190°F which i know is pretty good operating temp for the 4.0


Is this normal or is there something going on?
should i just cover part of the radiator to prevent excess cooling (which i cover up 80% of the rad on my 1988 dodge pickup in the winter and helps tremendously) or would that cause it to overheat?

 

I've had issues like that with mine as well where the gauge gives a clearly bogus reading then suddenly pops into the correct position, often repeating this behavior. It appears to be a problem with either the sensor or, perhaps more likely, the wiring. I just started this thread earlier this week, though I've not had a chance to do a closer inspection of the wiring.

https://www.cherokeeforum.com/f2/coo...delphi-254767/

 

Mine did that and it was the sensor. The sensor controls the fan, the gauge on the dash and the computer uses it for fueling so it can change drive ability a good bit. I don't remember the sensor being expensive so it wouldn't hurt to put a new one in.

 

Im going to start with a new sensor and go from there.

Ill post an update after some testing