oywa78

Hey guys, I'm a nube here, so my apologies if I unknowingly break any rules right off the bat. I've been having a problem relating to the AW4 (auto) tranny in my 1994 XJ, for about a year now. The first time I noticed this problem, I was seeing very erratic shifting, some gears would shift early and some would shift late. My idle was also higher than normal and kind of going up and down a bit. I found out pretty quick that my TP sensor had gone bad. I replaced the sensor, which stabilized the idle and brought it back down to normal (Just under 1,000 RPMs), but the shifting was still VERY off. The best I could tell, it shifted into 2nd gear too early and 3rd-4th gears were both pretty delayed (around 3,500 RPMs) and sometimes would not shift at all until I let my foot off of the accelerator, then they would manage to "slip" into gear. I did the TV cable adjustment, which through my idle out of whack again and the Jeep would not start. Did that same cable adjustment a couple more times and got it back to where it started and idled appropriately. The shifting issues remained. I decided that I would change the transmission fluid/filter, since it was admittedly long overdue for that service. I figured once I was in there, I would pull out the solenoids and test those. I drove it around for a bit with the erratic shifting, before I got what I needed to do the tranny work, until one day I was at a stop light and went to accelerate and it wouldn't go anywhere. RPMs shot way up, but it wouldn't go. I coasted it into a gas station parking lot and poked around, to find that I blew the damn TP sensor again. I replaced that sensor with another Duralast sensor from Autozone, since the first one I got from there was still under warranty. All in all, I had to replace the TP sensor THREE times, because whatever is going on seems to keep blowing these sensors, which adds up pretty quick at $55+ a pop. Last week I got into the transmission. Changed the fluid (did NOT flush it), changed the filter. Cleaning out the pan, I noticed very little metal fragments on the magnets, everything seemed pretty dang clean, compared to others I've seen. I pulled out all three solenoids and tested the resistance, which they all checked out at about 12.4 OHMS. I have been told by several people that they should be in the 11-15 OHM range, so they all passed that test. I checked the mechanical function by hooking them up to my battery and they all clicked as they should. I reinstalled those, filled it up with new Dexron3/Mercon. As I've been driving it around for a week, 1st-2nd seems to be much better now, but 2nd-3rd and 3rd-4th are still delayed (3200-3500 RPMs) and occasionally I'm still having to let my foot off the accelerator for it to shift. In my research, I came across the TCU as a possibility, except the 1994's don't have a TCU. I'm worried about this issue blowing out a FOURTH TP sensor at the most inopportune time, so I will be buying another one to keep in the glove box as a backup. At this point, I'm wondering if the transmission is just shot, or if there are any other things I should be considering that I may have missed. Again, the TP sensor and TV cable adjustment have both been done several times each. I really cannot afford a transmission and this is my only vehicle, so I'm REALLY hoping here can offer me some miracle advise to save my *** haha. Thank you in advance. Mike

MKP

Just a wild guess really, but check the grounds, especially the woven metal one at the back of the engine. Those are known to rot. I wonder if it trying to ground through the TPS. AW4 is a great transmission, but it's a bugger when it has electrical gremlins.

lawsoncl

The TCU is under the passenger side of the dash below the glove box, but it's rarely the problem. Have you tested the TPS that it changes smoothly and has a good ground? It's one of several important grounds that land on the passenger side of the block. I recommend cleaning that grounding point either way.

Reving up and not moving points to a bad #1 solenoid or wiring, which leaves you in 4th.

Roler

Have you tried shifting through the gears 'manually'?

cruiser54

try this. Free and easy. CRUISER'S MOSTLY RENIX TIPS

TRANSMISSION CONNECTOR REFRESHING

OCTOBER 30, 2015 SALAD 29 COMMENTS



Over near the transmission dipstick tube are 2 rather large connectors. One is black and goes to the NSS and the gray connector goes to the transmission itself
. These 2 connectors carry all the info between TPS, TCU, NSS, speed sensor, and transmission solenoids.

Unplug each one, visually inspect for corrosion or bent pins, spray them out with electrical contact cleaner and plug them back in.

Additionally, if your Jeep is an ’87 to ’90 Renix, it’s always a good idea to reach up under the glovebox area and unplug the connector to the TCU and spray it out along with the receptacle of the TCU. While you’re there, find the fuse right in that area for the TCU. Remove it and spray out it’s receptacle and clean any corrosion from the fuse.

Revised 1-31-2016

oywa78

"Just a wild guess really, but check the grounds, especially the woven metal one at the back of the engine. Those are known to rot. I wonder if it trying to ground through the TPS. AW4 is a great transmission, but it's a bugger when it has electrical gremlins."

I have wondered about the wiring, particularly the grounds, being it's a 1994 and I've never really checked any of that in the 11 years that I've owned this XJ. I guess I have had a hard time envisioning stuff like that just going bad all of a sudden, but I suppose it's just like anything else. We're going through a pretty nasty stretch of weather here and I don't have a garage, so as soon as things clear up a little I will definitely begin checking the grounds, as well as all other related wiring. If there was a grounding issue, then would that throw a code for that circuit at all?

oywa78

"The TCU is under the passenger side of the dash below the glove box, but it's rarely the problem. Have you tested the TPS that it changes smoothly and has a good ground? It's one of several important grounds that land on the passenger side of the block. I recommend cleaning that grounding point either way."

Someone suggested I look at the TCU a bit ago, so I started looking around and discovered that mine (1994) apparently does not have a TCU? I can't remember if it's the 1995 or 1997 XJ's that started using those.

oywa78

"Have you tried shifting through the gears 'manually'?"

Are you talking just with the shift lever or some other way? I have put the gear lever into all the gear positions many times, but I'm not really sure how to shift the AW4 manually while driving, what's the procedure for that? Thanks

oywa78

@cruiser54 Thanks for the tips! Those are some quick and easy things to do, so I will do that ASAP and see if anything improves. I went looking around for the TCU a while back and could not find it and, apparently the 1994 XJ's do not have a TCU? I'm a little curious if I may have been misinformed, so I will take another look under the dash.

cruiser54

They have TCUs!!!

Not sure when they went away from TCUs and incorporating them into the PCM, but 94 has one.
When you find it, note if the harness plug and the TCU's receptacle are the same color.

oywa78

"They have TCUs!!!

Not sure when they went away from TCUs and incorporating them into the PCM, but 94 has one.
When you find it, note if the harness plug and the TCU's receptacle are the same color."

Alright, thanks Cruiser, I will definitely take another look as soon as I can and reply back.

Roler

Yes, start driving in 1-2 and then manually shift it up to 3, and then D. Like you'd be driving a manual.