Erik Hoeffner

Just replaced the thermostat in my 91 XJ, engine light comes on 12 hours later and dies on me on the road twice. Now I get a code "22" saying "faulty wiring to coolant temp sensor or bad sensor". What can I expect as far as this affecting the drive/car and how do I go about replacing it ASAP?
Also my RPM's are fluctuating sometimes while going the same speed, In neutral going down a steep hill the RPM's will stay the same as if I was on the throttle. And when I am slowing down to stop it will downshift to the last gear a few seconds late and it revs up right before downshifting. Is this related to the sensor, or do I have another issue?

ZINGGG

Go get a new temp sensor. They're only about 20 bucks and can be found at basically any auto parts store and are easy as cake to replace. See how it helps. But it sounds more to me like your throttle position sensor

Erik Hoeffner

Alright thanks for your input once again haha. Tonight when i drove it the engine light was off and it stopped doing anything RPM related-at least for 13 miles of my 20 mile drive, then the engine light came on and it went back to acting up, though not as bad as before. So I am guessing all my issues are related to the sensor; I have had people tell me the RPM's acting up is the ECM pumping excess fuel into the engine to keep it heated, while the electric fan constantly runs to counter act it overheating. Since the ECM has no idea where the temp is at I suppose thats how it tries to create a "midpoint" of heat..?
Anyway I'll put this in tomorrow and post on the results...
I hope and do not think it is the TPS, as that was replaced only 2 years ago.

Erik Hoeffner

...Also, do I just unscrew the old one and screw the new one in? Do I need to apply any silicone etc. to seal it?

ZINGGG

Yeah that makes sense. So try that sensor. And yes, it's that easy. Take off the electrical connector to it, unscrew it, and then screw the new one on. Make sure to have the new one right there when you do it though cause these sensors sit in coolant so when you unscrew the old one, coolant might try come out. So just be ready with the new one right away. The only thing you might want to add is anti seize to the threads of it just as reassurance that it'll unscrew just fine if you ever need to replace it again. No silicone needed though, it won't leak.

kjc

"...Also, do I just unscrew the old one and screw the new one in? Do I need to apply any silicone etc. to seal it?"

Lefty Lucy then Righty Tighty, ya..

I don't 'think' it needs a good ground for the sensor, but you're plugging up a hole with a threaded bung. I'd use that copper sealant on it.. good ground if needed and no leakee.

Erik Hoeffner

Alright just got the job done. Didn't realize it was THAT easy. Took like literally 5 minutes. I didn't have any anti seize on hand so i just put it in as is; but considering how easy the old one came out I'm not to worried it would get stuck.
When I drive to work I'll see if its all good, the engine light was off again when I started it this morning, I guess the old sensor tried to work in the cold but goes all wacky after it warms up...I wonder if maybe cleaning it would have made it work..?

ZINGGG

Haha yeah told you it was easy as cake. No big with anti seize. Really not needed but it's always good to have reassurance. Well depending what the old one looked like, taking it out and cleaning it could have helped. But a new part will always work better than an old, cleaned part. Hope it works for ya!