Hello again....
I'm getting some intermittent hard start/idle issues with my heap and they seem to coincide with the temp gauge falling to 0. Is it the same sender for both the computer and the dashboard gauge on the 1997? If so, I think I need a new one ! (after checking the wiring).
Thank you!
Morat

 

'97 up have 1 coolant temp sensor.....it's located in the t-stat cover. The CTS signals the ECM, the ECM signals the temp gauge needle where to point.

 

Brilliant, that sounds exactly right then.
My temp gauge swings down to 0 intermittently, I also get a poor idle, slow return to idle from revs, hard hot start and a mis/stumble when opening the throttle from idle.
The Jeep was doing all of those things today when we had the hood up, then suddenly it just started behaving perfectly. I had my head in the engine so I couldn't be sure that the temp gauge had just sprung back into life but I'd bet quite a lot that was it.

I'd been mislead by my old BMW which had separate sensors for the gauge and the computer so I had ignored the temp gauge dropping as irrelevant. Right then... ordering time!!!

Thanks so much.
Morat

 

I had the same problem, same symptoms. I have to remove the connector and clean the metal contacts on both sides of the connector. When I bought my 98 5 years ago, I took it for a test drive. I shut the engine off and tried to re-start. the engine choked, bucked, stuttered and finally started. I brought it back to the seller and duplicated the problem. He cursed and muttered, popped the hood and pulled the temp sensor connector, pushed it on and off the sensor several times. The jeep started and ran perfectly. This has happened twice more in 5 years. A permanent fix for me would be a new connector AND a new sensor.

 

I was unaware that the CTS would cause engine running problems. We've had the CTS unplugged on our '98 and 2 things happened: 1. efan immediately defaults to "on/run" and 2. a CEL/code is set. Our XJ starts/runs fine with the CTS unplugged.

 

Now that's worth a try! Thank you

 

The ECU senses a problem with temp sensor and operates in "open loop" default settings which would cause your jeep to start and run in safe settings, but not optimal for fuel economy or clean emissions. Just a thought.

 

Hum, I thought the up stream O2 sensor determined open/closed loop. The system does enter closed loop way before coolant temp is anywhere near operating temp, no?

 

True, but when the temp sensor is not connected, the ECM sees a cold engine and changes to engine warm-up mode, which is an open loop state. For the 98 cherokee, this is further explained on pages 14-26 and 14-27 of the factory service manual.

 

Problem solved
Pulling the connector off to test the sensor was enough to get it working again. I guess the pins were a bit messy. I've got some contact cleaner on order so I'll give it a proper clean soon.
Simplest fix ever!
Thanks folks