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Washed Engine, Now Tranny Won't Shift

E

Eliminator89

NAXJA Forum User
Location
Winona, Mn
Just recently bought a '90 4.0/auto Cherokee. Seriously soiled engine. Engine degreaser + power washer = no shift.

Have read through the search feature that I probably wrecked the TPS. Also read that unplugging the TCU fuse would enable me to shift manually. No joy.

Tranny still won't shift working the lever manually. Then read that it won't shift until higher rpms are reached. Is that right?

Have a new TPS but won't have a meter to properly adjust until tomorrow. Will install new TPS when I get the meter. I have the FSM for the '89 model year. Should it still be applicable for the '90?

Opinions?
 
The Renix fuel manual covers years 87-90. if this is not what you have then PM me and I can hook ya up. It covers the entire renix setup, both manual and auto tranny.
 
You pulled the fuse for the tranny that's in the harness, right up next to the computer? If the computer has no power, you'll get 4th in (D), 3rd in (3), 1st in (1-2).

While bad output shaft speed sensor will cause it to not upshift as well, I'd suspect the TPS since that is vulnerable to pressure washing. For now you can just install the new TPS in the same position as the old one and adjust it using the meter later.
 
Not sure about this, but here is a shot in the dark..... I am fairly new to jeeps so this may not be the case. I once knocked a vaccum line off an explorer going to the trans and it did not shift correctly. Does the xj trans have any vaccum lines going to it?? I am not sure myself, but it may be worth a look
 
Nope. No vacumn lines. It does have a throttle cable, but that only controls the hydraulic pressure in the tranny which affects shift firmness. The tranny computer controls the shift points.
 
Power washer = 1100 psi. Weathertite connectors = rain proof, not power washer proof.

Disco the connectors, spray them out with WD40, resilicone grease them.

High pressure washers do this all the time, to a lot of cars. People get towed from the car wash frequently for this for no starts.. Even the used van dealer I buy from did it to my wife's new to us van. Experienced mechanic, just didn't know it.

Before you replace anything, dry out the connections. It's a lot cheaper.
 
Couldn't get the meter today (didn't work, spent the morning in the emergency room-long story, I'm fine, my big toe is a little worse for wear but I'm fine). Going to install the new TPS anyway.

The fuse I pulled was a 7.5A in the fuse block, '89 FSM indicated it was for the TCU. Still no shift by working the handle manually. Connectors for the drowned TPS looked to be dry.
 
Ok, new TPS fixed it. I'll get it properly adjusted tomorrow after work but for now the tranny is shifting again. I do wonder why I couldn't shift it manually though.

Got a Borg/Warner TPS for $33 and some change. The local O'Reilly's has a low price match policy. I found a cheap China made TPS at another store and they matched the price. :)
 
Eliminator89 said:
Couldn't get the meter today (didn't work, spent the morning in the emergency room-long story, I'm fine, my big toe is a little worse for wear but I'm fine). Going to install the new TPS anyway.

The fuse I pulled was a 7.5A in the fuse block, '89 FSM indicated it was for the TCU. Still no shift by working the handle manually. Connectors for the drowned TPS looked to be dry.
Click to expand...

Poor labeling. That fuse is for the backup lights and the power/comfort select switch. It doesn't actually feed the TCU.
 
Left the hood up last night and it snowed lightly - guess what, the tranny won't shift.

Is the TPS that sensitive to moisture - in a 4WD car?

I think I just found out it is.
 
They seem pretty sensitive to pressure washing, especially the newer models. I have trouble picturing a little snow hurting it as I have washed my engine with a gentle hose with no problem. I have heard of people successfully drilling a small hole in the sensor case and flushing with contact cleaner.
 
Napa = 38.99, AZ = 77.99. Contact cleaner = got some (electrical, not for the hard lenses I wear. :eyes: ) I'll give it a try.

Leaving a drop light under the hood next to it overnight did nothing.
 
I didn't reply to the thread with the intent of replacing MY TPS. I did tho.

Works just fine with a new one now. Didn't match the volts yet, just the marks on the TB where the old one was. Started right up and idled right where it had, shifted fine.

If I ever let on I thought problems with the TPS were more about the operator, I was right, adn in this case it was me. Don't even let snow fall on it. I'm trying to imagineer a splash shield for mine to install when I get around to setting it with a voltmeter.

Something out of a milk jug or turkey pan should do . . .
 
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