MJ auto transmission help

[Bounty__Hunter]

So today I got my '88 MJ running that I picked up for $150, only
took a new fuel filter luckily. It's a 4.0L auto shortbed 4wd with
bucket seats and sunroof, body is pretty straight and solid. I
bought it knowing the owner was having transmission issues.

The auto (AW4 I think) doesn't want to upshift from 3rd to 4th. I
checked the fluid and looked good. I think somebody mentioned a
sensor on the engine that could affect this, anybody know?

Will a '93 AW4 bolt right in?

All help is greatly appreciated, hopefully this thing will be
lifted, locked, and on the trail soon.

Thanks,
Chris

 

[MudderChuck]

I´ve been playing with shifting issues in my 88 on and off for more than a month. It´s real close to being right now.
Most of my problems were coverter lock and unlock (couldn´t make up it´s mind) a certain speeds RPM´s. But noticed my shift points changed, as I adjusted and serviced the system.
Might as well start with the TPS adjustment, even if it isn´t the solution, chances are it´s out of adjustment.
Do you have the FSM or alldata?
After you get the TPS and CV cable adjusted, pull the TCU fuse under the dash and try shifting it manualy, should hit first gear, third gear, fourth gear, neutral and reverse.

 

[Bounty__Hunter]

I didn't know the TPS was adjustible on this engine, and don't know anything about the CV cable. Only FSM I have is for the '95 YJ.

 

[jps4jeep]

I would also start with the TPS!

is there also a mechanical shifter detent on that transmission or is compltetly electronic?

 

[MudderChuck]

The CV (control valve) cable adjustment is pretty easy, there is a thumb sized tab near the throttle body, push the tab in, slide the inner part of the extension sticking out the end up the adjuster in and then with your thumb. push the throttle all the way open. The sleeve sticking out of the adjuster (with the cable from the transmission sticking through the center), will click out a notch or two and the TV (transmission valve) cable. The cable has a few different names, but what it does is connect a hydrolic pressure valve to the throttle and also operates kick down or passing gear.
Dingus had an 88 or 89 FSM, for download, may be something in search.
After the TPS adjustment, the next thing is to pull the fuse and see if it shifts manualy, seperate the software from the, hardware.
If it´s hardware it could be the wiring, the contacts (common) or the solenoid valve in the transmission (not that big a deal to change, but expensive new). There are some continuity checks and a connector view in the FSM, makes troubleshooting with and ohm meter possible.
My best guess is the connector or the shift contacts are corroded.