Howdy! So I've been chasing this shifting problem around since October of last year, for about 10k miles or so. It comes and goes and I'm at my wits end, but I'm pretty new to wrenching and cars and I have no clue where to start with electrical. 1996 2wd, 4.0, AW4. 220k miles on the clock. No CEL or codes. The jeep is my DD.

All of these seem to be randomly occurring with no particular rhyme or reason, both warm/at operating temp and from cold start, sometimes multiple will happen on one drive and sometimes none happen at all:

• from a dead stop, sticks in 3rd and I have to either floor it or manually shift to 1/2 to get going
• from a dead stop, starts in 1/2 (proper gear) but will not shift up to 3rd
• late shift from 3 to 4/OD
• TC will not lock up, or will lock up and then unlock and not lock up again on the highway (regardless of braking/lack-thereof)
• drops out of 4/OD, RPMs will kick from 2.5k to 3k+ going 65mph (2.2k rpm is my normal w/ TC lock-up), will sometimes shift back into proper gear on it's own
• falls out of gear from 4/OD and will almost redline. Will not shift again until I pull over and restart.

I can shift manually up and down gears. All problems go away when I pull over, put the car in park and restart the engine. Sometimes they start again, other times they go away for a few cycles.

Things I've tried (from oldest to most recent):

• replaced the tps in december with mopar sensor from dealer
• drain and filled atf 4 times in february, fluid looks good/red, doesn't smell burnt, reads just over full (checkered area) with engine hot and idling in neutral
• cleaned all grounds
• cleaned connectors w/ electronic cleaner spray at the tps itself and the plugs by the dipstick
• tested tps from throttle close to open, went up and down smoothly based on throttle position, but read overall low.
• replaced tps fuse under hood (had some corrosion) - this seemed to fix my problem momentarily, throwing a "high tps voltage" code when I replaced it. I reset the tcu(?)/disconnected the battery and the code has not reappeared in the last 200 miles. This fixed the low tps voltage problem I had when I back-probed the tps but I haven't checked it again since I did this two weeks ago.
• (Eta: just checked it again, with key in ignition set to 'on', TPS voltage ranges .84-3.8 closed to WOT. This is low, right? Full 5v in, ground is good)
• checked connection at the brake switch (also, my brake lights work fine)
• adjusted the kickdown/tv cable

The internet seems to be pointing at either a tcm/tcu or solenoid issue? Unless my tps is just dead enough to only work sometimes. I can manually shift through the gears, so my solenoids... should be okay? What else should I be looking at? I know I can check the plug at the dipstick for resistance (i'm just not sure... how? I'm supposed to set the multimeter to 200 ohms resistance, and I should be looking for 12-18 according to another post I read? Is this correct?).

What about at the tcm/tcu? What is the difference between a tcm and a tcu anyway? Mine is under the passenger-side dash, but I've been having a hard time finding a diagram for the '96 to probe it. I've only really found one for the 97'+ found under the driver - are these the same? I've seen on the older ones, they have their own fuse. I tried to check mine but didn't see one, should there be one and I'm missing it?

Any help would be appreciated!


Other issues I'm having/have had recently that may or may not be related:

• power steering pump blew and exploded all over the engine bay last august - gear oil sitting in connectors maybe?
• intermittent stumble on start/random crank no start (both warm and cold start) - ongoing, maybe causing shorts, voltage issues?
  • replaced cps the other day (napa echlin)
  • ignition coil cracked and died last summer and I replaced with cheap part, ngk on the way to put in when I change my sparks/wires/dist cap/rotor this weekend - will also check dist. pick-up. Last spark plug change/tune-up was almost exactly 30k miles ago.
  • starter issue? Replaced starter relay just in case. Alternator seems fine and battery reads at 12-15v consistently, have not tested under load. Battery purchased last august.
  • fuel pump primes fine, fuel at rail (have not checked pressure with a gauge but the fuel is there)
• overheating/heat sink/no electrical fan - overheating components leading to heat failure of tps?
  • I have a new fan and temp sender (thermostat side) on the way
• AC pulley bearing going out - probably not related I just wanted to add it to the list lol

 

Lots of issues....if it starts in 1/2...meaning you can engage starter with the shifter in 1/2, that means your NSS is no good or misadjusted. First step to fixing your problem is to fix that

 

Sorry, I meant "starts from a stop", not a cold start. I've never tried engaging the starter in anything but park.

 

Solenoids can be tested without removing the pan.
It's done using the connections I recommend cleaning in Tip 10 at www.cruiser54.com.

 

I've seen a couple diagrams around for which pins to test for the solenoids, but they're all -'95 or '97-'01. Do you know which one I should be looking at for a '96? I think it should be the '95 one, since I have a separate TCM from the ECU, does that seem right?
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All XJs had separate TCUs.

You should be able to search and find the diagnostics for your year.

 

To Update: Tested all my solenoids at the tcu, tested fine, hit the connector with some more cleaner and plugged it back in. I must have not plugged it back in properly the first time or something because the problem hasn't come back.

Seems the main culprits were the tps fuse corrosion and dirty connectors after all.