A new TPS didn't fix the problem... any ideas?

I have a 1990 4.0 AW4 Cherokee. A few weeks ago I took off my throttle body and cleaned it real good with some carb cleaner. About a week or two later I notice that the Jeep intermittently acts like it doesn't know which gear to go into. It has only done this a few times..

A couple weeks later, I got stuck in mud real bad, and it took about 30 yanks to free the Jeep. Now over the next couple of days, I noticed the Jeep acting funny again.

It's real hard to describe what it does, and I doubt someone would really notice it if they didn't drive this Jeep daily. While accelerating, sometimes it will act, and sound, as if the gas had been let off. It has been doing this quite a bit over the last week. I have not seen a change in the RPMS while this is happening, but I do feel it happen throughout the Jeep.

Here's a pretty crude example that may describe what I'm trying to say better... when accelerating, the engine goes like this normally:

(pretend "grrrrr" is the sound of the engine...)

Grrrrrrrrrrrrrrrrrrrrrrrrrr

Now when this happens, it seems to sound like:

Grrrrrrrr--rrrrrrrrrrrrrrrr

Sorry if that looks confusing, but it's the best way I can think of to describe what's happening.

Going with the advice from the Jeep forums, I had my throttle position sensor swapped out with a new one from Napa.

The problem still remains... any ideas?

I have a memory of my 89 doing this years back- it ended up being a vacuum line cracked. The "defrost comeing on by itself" problem didnt happen for several weeks later though. always happened on acceleration- sounded like the engine would cut power for just a few seconds unless you were going up a steep grade...then it wouldnt kick down at all.

Just for kicks, run a vac test- go buy a quicky cheapo vac guage and plumb it inbetween the manifold and the vac bottle- run the engine and look at mr guage (chek for unusual bounceing at idle)- when you shut it off, see how long it holds vacuum...if it disapears quickly, find that leak. if it holds for a few seconds or more, look elsewhere.

I say vacuum also, check for the hissing sounds durring idle.

now I found this Fix diagnosing a Trans that wouldnt come out of 2nd gear, on most Xj's there are a few wires that are ring terminal'd and grounded on the top passenger side of the bell housing. What i had happen was no matter what this 92 Xj would not come out of 2nd gear, acted like a internal trans problem that had foced it into limp mode. would got to park reverse and neutral fine, but any forward gears would force it to second and it would stay there. the fix was the fact that one of those wires is a reference gorund for the tps, disrupt it and the comp donesnt have a signal to run the trans line pressure off of. might be something to check. you should be able to see them easily, never know.

My Jeep the almost the exact same thing before, turned out to be a vacuum leak. Does your Jeep still idle fine ?

Yeah the jeep idles just fine, except it's a little high since I adjusted the screw out too far.

I don't suppose it could be a problem with the transmission mount, could it?

Where should I check for vacuum leaks?

I would check for vacuum leaks as well, but if you find none and you had already change your TPS and it is good thur out its range of motion then I would check your ICM sensor, this what controls the Idle of the motor. Maybe gas filter?.

What i am understandingis that your tranny doesn't shift right, period... not shifting into the next gear. If that is the case then i would say you might need to change your tranny fluid and filter and while you are at it you might as well check the solenoids. ( these solenoids is what controls your shift points).

The solenoids is controled by the TCU and is located on the side of the valve body. To test the solenoid resistance you will need an ohmmeter. Connect the ohmmeter leads to the solenoid mounting bracket and the other lead to solenoid wire terminal, the resistance should be 11-15 ohms. anything above or below that range then it could be it. Just a thought, it sounds like something i had experiance.

BlueKnight said:

I would check for vacuum leaks as well, but if you find none and you had already change your TPS and it is good thur out its range of motion then I would check your ICM sensor, this what controls the Idle of the motor. Maybe gas filter?.

What i am understandingis that your tranny doesn't shift right, period... not shifting into the next gear. If that is the case then i would say you might need to change your tranny fluid and filter and while you are at it you might as well check the solenoids. ( these solenoids is what controls your shift points).

The solenoids is controled by the TCU and is located on the side of the valve body. To test the solenoid resistance you will need an ohmmeter. Connect the ohmmeter leads to the solenoid mounting bracket and the other lead to solenoid wire terminal, the resistance should be 11-15 ohms. anything above or below that range then it could be it. Just a thought, it sounds like something i had experiance.

Click to expand...

No the transmission shifts fine usually. Other times it will sort of jerk itself into gear, but I think that is a problem with the mount. The sort of power loss I am getting only happens intermittantly.