Green Mesa XJ

Hi, Sorry if this is a duplicate topic.

Need some help diagnosing a problem with our 1992 4.0 4x4 automatic Cherokee.

In laws needed it to move some stuff too big for their car. They drove it a few hundred miles over the last week.
Just got a call with them on the highway apparently it is losing power. Almost hesitating. Feels like it goes into neutral then back to OD.
If he shifts from neutral to OD it seems to run fine again. Or stomps the gas it down shift and accelerates fine, cruising again in OD at 65 no trouble.
In neutral the engine is idling fine.
Last word was it drove the last 40+ miles after they called me with no trouble then felt like it did it again getting off the interstate.

Fluid level in the transmission is good, transfers case and transmission have fresh fluid less than a year oil.
Fuel pump is a Bosch replaced about year and half ago.

About a year and a half ago it started doing a weird up shift down shift when trying to accelerate on to interstate. like it would shift to OD too early then down shift again.
I adjusted the TV cable and it seemed to go away. It never did this problem but under certain conditions which weren't often.

My first thoughts were the torque converter or transmission failing, possibly the transfer case. I know it has transmission computer of some sort not sure what it actually controls. I don't think the TV cable out of adjustment could do what they describe. When I test the fuel pump when I installed it, it had good pressure.

I'm hoping some reading this has a "oh yeah " moment and knows exactly what this is.


Thanks in advance for your help

Radi

I'd take a peek at the TPS and also the brake pedal switch. The TPS has a lot of input into shifting decisions and the brake switch can unlock the torque converter.
What kind of trans fluid did you use when you changed it?

Green Mesa XJ

I'll check them when I get a chance to get out there. It has a water leak somewhere so the break switch could have gotten wet. What should I look for with the TPS?

The fluid I can't remember off the top of my head, but when I was doing the maintenance I did look up which fluid was recommended.

Radi

Hopefully you used Dex/Merc fluid? Some users report slippage with ATF+4 despite Chrysler's recommending it.

The TPS- they can develop a flat spot, often where the throttle commonly sits (highway speed, etc). That fools the PCM into thinking you took your foot off the throttle with interesting results.
You can check with a voltmeter between the center and ground wires. Operate the throttle by hand very slowly and watch for a smooth, steady increase in output voltage. No dropouts or jumpy spots. Key needs to be ON, engine OFF.
If you replace it, get the part from a dealership if you can. NAPA seems OK as a second choice.

Green Mesa XJ

I checked my order history. I replaced the TPS in August 2012. It was a onix-Ada, but I'm not sure who it actually was by. I've had problems with parts order through Amazon being brands other than what was ordered.

I don't believe the oem TPS failed but changed it and the cps while doing 20th anniversary pre-maintenance.

On the fluid I really don't know there is a spare bottle in the jeep so that will tell the story there.

Green Mesa XJ

Looks like the factory TPS is part # 4761 871AB .I've been searching with this # without much luck. Has it been superseded ?

Green Mesa XJ

Want to say thanks to Radi! Looks like you advice was right on the money

Ended up replacing both the Brake switch and TPS. I think the switch was the problem, either out of adjustment or shorting.
Replaced it with a factory part.

The TPS I wasn't sure about the readings (probably my fault) so ran down to napa to get replacement just to be sure, hard time finding a factory part online.

On the test drive I could do all the little converter test, I could feel the converter locking and unlocking. 100 miles on the highway getting home and she never missed a beat.


The only time I came close to what they described as happening was testing the converter at highway speed. No idea if this what what they felt or not.

BTW Fluid was Dex/Merc.

We may take the jeep on a longer highway trip this thanksgiving to test it.

Anyway thanks again for your advice it really helped us out

Radi

Glad you got it fixed!

Green Mesa XJ

Just wanted to say thanks once again. The old jeep proved itself twice more with long highway trips (500 to 600 miles), no problems.