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AW4 shifting erraticly

90Blue_XJ

90Blue_XJ

NAXJA Forum User
Location
In yer postz fixin yer spellinz.
When I'm cruiseing along at various speeds anywhere from 35-65 the transmission will downshift by itself with a steady throttle on level ground (the only type ground around here) I checked the fluid (OK) TPS (OK) and don't know where to check next. The AAMCO guy said its electrical and wants to rebuild it. ( I suspect he just wants to hold my plastic for awhile) It never acts like it's slipping or there is no burning smell. All connections have recently been cleaned when an engine transplant was performed (8 months ago) This problem started on a long trip of 1600 miles and has continued off and on.
ANY IDEAS???
 
What year, model is it?
 
I suffer from the same problem. I havn't done the TPS yet or even checked it for that matter, but I found a huge improvement after I adjusted the TV cable back to factory spec. It seemed to have solved half the problem. Soon I'll get around the testing the CPS, for now I'm not driving the XJ much so it's not an issue.
 
Sorry Ecomike it is a 90 4.0 aw4 242

What's a TV cable other than for your TV veiwing pleasure. Not being rude just uninformed.
 
it may be electrical, but it's highly unlikely it's the solenoids in the transmission, so don't let him start digging into the tranny. the problem is most likely with the TCM or a related sensor. Try a junkyard PCM and maybe a new TPS even if yours tested okay.
 
mikeforte said:
Sorry Ecomike it is a 90 4.0 aw4 242

What's a TV cable other than for your TV veiwing pleasure. Not being rude just uninformed.
Click to expand...
the TV cable (aka the throttle valve linkage). Do a search and you should find the information you need to know. Setting it back to factory spec is probably a good idea as the cable stretches out after a while. Jeep built in an automatically adjusting doohicky that just requires you to take 3 easy steps. A search will turn up how to do it.
 
Thanks I now feel a little less stupid but a search failed me when I looked for PCM or TCM but I guessed TCM= transmission control module maybe but still can't find where to look. Damned Haynes manual might make a good source for paper to start a fire.
 
sjx40250 said:
TCM's rarely go bad. Only heard of one instance.
Click to expand...
Where are they located in the whole mess under the hood & am I right in my guess(Transmission control module)?
 
mikeforte,

The three letter acronyms like TPS do not work in the search engines here at NAXJA. I hear it works if you google search "NAXJA +TPS", or just search "Throttle Position Sensor" here.

Be sure and read the FAQ's fourm on searching.

Your 1990 should be a Renix, which uses the TPS that has two connectors on it. It actually has, is two variable resistors coupled together, so you need to check the readings at idle, and WOT (wide open throttle) and then check that the reading changes smoothly with movement of the throttle cable on both sides (both connectors) separately.

The how to steps are posted here in several prior discussions in this forum, and are listed in the FSMs (Factory Serviice Manuals) found on other sites. Try Googling "Renix Jeep Factory service manual" which should help you locate an online version.

Also, be sure to search "throttle linkage transmission adjustment" here for the procedure on adjusting the linkage between the transmission and the throttle body. Doing one or both should fix your problem.

Can you describe your down shift problem in more detail, speeds, RPMs, before and after?
 
hmm, pretty strange problems still with my shifting today--
I drove out to a local logging road to do some mountain biking, had horrible up/down/mis-shifting the whole way there and thought "oh crap it's getting worse--f*ck!". After the ride I went to the local hardware store to get a new multimeter to readjust the tps..and the whole way there it didn't miss a beat, shifts like it was new. I picked up the new multi meter, then I drove home another 30km and didn't have a single shifting problem. I can't figure out what it is...but maybe I'll just chalk it up to "a jeep thing". All I did differently was rally the jeep up the logging around at 60km.h for a bit, and after that it seemed to shift like new.
 
BrettM said:
it is indeed rare. my money is still on the TPS, even if it tested right.
Click to expand...

X2. I had a similar issue with mine not wanting to stay in 4th/OD. It would also sometimes get real jerky once it got good and hot and I was taking off from a light. New TPS did the trick.
 
clunk said:
When you put a new TPS in, did you use a multimeter to set it up properly?
Click to expand...

Yes but I can't remember the readings. I was still in Georgia and a friend w/ a FSM talked me through it as he was overseeing the job. He said everything was up to the info in the FSM. Still noone has said if TCM is the same as TPS or does it mean Transmission Control Module?
Still in the dark about this!
 
TPS is the throttle position sensor located on the throttle body. TCU is the trans computer located under the passenger side of the dash. My bet is the TPS sensor. A 1990 TPS sensor has two outputs. The square connector is the one for the tranny computer and is the one you need to check. The voltage (or ohms if measuring unplugged) should swing smoothly between the extremes without any hiccups or bad spots. THe TPS is the usual culprit for erratic shifting.
 
I adjusted my TPS earlier today. Even though it was *hardly* out adjusting it back to spec seemed to make a HUGE difference in my shifting--Purred right along with no skipped shifts or missed shifts.. I also cleaned the IAC valve at the same time. When I started it back up it idled rough for a few seconds then settled down--I assume this was because I cleaned off the IAC sensor with electic parts cleaner and it burned a little hot for a second. Seems as though my "mis-shifting" problems are taken care of...Ive found "solutions" in the past--so I don't know if this will last very long or if this is just another adjustment that will last a half hour...
 
EXCELLENT I will check it again today. I have not checked it in about 6-8 months. Maybe it is the guilty party. I sure hope so. Thanks everyone for your input.
 
I should also mention that it might be helpful to clean the contacts on the TPS--get some electrical parts cleaner for the job. Undo neg. terminal of battery, trace the wires from the TPS back to the two plugs, clean both positive and negative terminal on the plugs with several shots of electrics cleaner then put them back together. While you have the power cut to your jeep, you may as well go ahead and spend a few minutes cleaning the IAC vavle, it seems to get some gunk built up--electical cleaner will work fine for it, just clean the nub off at the end. Just unplug it, clean the terminals then undo the two torx bolts holding it on, pull it out gently give it a clean up then put it back in. It's a pretty sensitive part so make sure you use something sensor-safe to clean it and go gentle on it.
 
Thanks I will have to wait til monday afternoon because the wife (who is the boss around here) put me to work on the flower beds until after dark.
 
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