transmission issue

My girlfriend told me her jeep started doing something funny today. While driving (she was going 65 on the highway) it would make a clunking noise then shake and shudder. She said it happens when shes accelerating. I changed the fluid several months ago but didn't do the filter. I had this issue happen to me once several months ago also, but put TransX in the transmission and didn't have a problem until today. Could the filter somehow be causing it to do this?

sounds almost like what happened when my TPS went out. I have a 98'

it does have a random high-idle at start that wont go away or randomly wont start at all (cranks but wont start). I know the high idle is a symptom? Think it'll solve the other issues?

Crank, won't start, suspect CKP (CPS).

Random high-idle, suspect TPS.

Clunk and shudder under acceleration, usual suspects trans mount, engine mounts, u-joints, could be LSD w/o modifier. Time for a visual inspection under there.

Well I just got off the phone with her. She had to drive it on the highway and it would stall while driving, she would have to pull off, restart, and while accelrating it would shudder, clunk, then jerk like it was taking off again. I thought the TPS had an effect on the transmission, I would like to think its something simple like that before we pour money into it

IRPancake said:

Well I just got off the phone with her. She had to drive it on the highway and it would stall while driving, she would have to pull off, restart, and while accelrating it would shudder, clunk, then jerk like it was taking off again. I thought the TPS had an effect on the transmission, I would like to think its something simple like that before we pour money into it

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Lucky dog! Run to the store and buy some wine and candles, have her bring it over to your place, and then tell her it isn't safe to drive home and she has to stay over!

Just kidding. What concerns me is the engine stalling out, you need to determine that. Could be fuel starvation, loosing the CKP signal, etc.

What year, engine, trans?

sorry that might have helped! 88 4.0 AW4. I've been searching and came accross some info on the CPS, but it also listed something about the NSS and how the reverse lights not coming on could be a indicator of that being bad, which they will *sometimes* work.

I'm assuming its one of these things considering its all happening at once (or it would be just my luck!). I'm starting to think its the CPS because of the no start and cutting out, but could that also lead to the bucking? The high idle start it has is definately the TPS, but it only does it on occasion so I decided not to mess with it, I thought the TPS had a function with the transmission, could it being off make the transmission buck like that?

thanks for all the help so far!

she lives with me already, the problem is shes too far away from home now!

Yes, the CKP (crankshaft position sensor--located in the bellhousing) failing will give you a no-start condition (crank, but no spark) and the CPS (camshaft position sensor--located in the distributor) only effects the injectors timing and duration. Essentially the CKP is the only sensor that will KILL a Renix XJ, all other sensors and it will still run in some manner.

As in "bucking" if the engine is cutting out and catching then yes.

The TPS will effect the transmission and engine performance, will not KILL the engine.

The NSS (neutral safety switch) can not KILL the engine, it will only prevent the engine from cranking.

You may have a number of things going on. Do a search for NSS and you will find plenty of threads on how to remove, clean, dielectric grease, intall and adjust it. They run $120+, and the work is simple. Here is a link to JP Magazine article: http://www.jpmagazine.com/techartic...eep_cherokee_neutral_safety_switch/index.html

Thanks for the reply. Turns out it only stalled at low speeds in a parking lot, but it was 'bucking' at speed on the road. I drove it and experienced it, it felt like you hit a freaking animal or something, but then immediately keeps going like nothing happens. It only happened to me once while we went to get food but it happened to her 5 times on the way home. I'm not sure if the engine is cutting out or what, but what is my most likely culprit, if I have to throw even 100 bucks at it I'll most likely just sell it, it was a $1200 starter car for my girlfriend, now she has a job and its all highway, she wants something a little more fuel efficient and stable at speeds. I just want to get it figured out so I'm not completely dumping it in someone elses lap

Rent a fuel pressure gauge and get your base line numbers, then tape it to the windshield and see if you can get a reading when it is "bucking".

the bucking only lasts for a split second (more like a jerk, bucking implies it lasts for a while I guess), and it hits at random times that I dont even think I'd be able to look at the gauge quick enough.

Could be losing the CKP signal.

Unplug and plug the CKP harness a few times and make sure it isn't getting melted against the exhaust.

It could even be battery cables or ground. RENIX killer?????????? Ground strap from head to firewall IIRC?????

I dont believe its a battery issue, just because it cuts out for literally a split second then acts normal for a while. I'm going to go check the CKP harness, its near the back on the top right? Either way we're going to be selling it because of my girlfriends commute to work, I'd still like to get it figured out even though the people who might buy it probably want it for a trail rig more than anything and would invest more time/money into it. Appreciate all the help guys!