Auto trans not shifting.....

Gil BullyKatz · Apr 29, 2004

Can't seem to get my '88 4.0 to upshift out of 1st gear....
All started after washing the engine bay....

TCU?

any other electronics I could've compromised?

TIA

RINGKONG · Apr 29, 2004

Gil BullyKatz said:
Can't seem to get my '88 4.0 to upshift out of 1st gear....
All started after washing the engine bay....

TCU?

any other electronics I could've compromised?

TIA

You screwed up your TPS buy getting it wet...

Gil BullyKatz · Apr 29, 2004

doubtfull....replaced 3 tps in 6 years..never did anything like this....

bueller...

bueller...

bueller?

XJTripp · Apr 29, 2004

Perhaps the Neutral Safety Switch. I believe it also is responsible for "telling" the TCU what position your shifter is in. It is down on the side of the Trans. If got messed up, your TCU may not sense that your shifter is in D. The TCU is under the dashboard, it should not have gotten wet. Maybe the power feed to it is messed up, but I thought that when you interrupted power to the TCU, the trans behaved in a fully manual way. There are even links that discuss installing a switch in the TCU power feed to get the trans to hold in low when you shift to the "1-2" position.

bbell90xj · Apr 29, 2004

I had the same thing happen after my son-in-law washed under the hood of my 90xj. It was the TPS, thought my transmission was going out.

old_man · Apr 29, 2004

It's got to be the TPS. The computer is under the dash. The TCU is really two different units combined in one housing. One half gives the ECU info for the fuel injection and timing, while the second half gives the tranny info for shifting. Most failures of TCU's envolve the half that controls the engine, which is probably what you experienced before, but if the other half got wet, the symptoms would be totally different.

Gil BullyKatz · Apr 30, 2004

Got home from work after using the wife's car for the day...Spun the jeep around the block a few times...

It does shift, but at about 4400 rpm, where before it did at about 2000

What controls the shift points?

All my previous problems with the TPS were intermittent non-starting... I swapped out the oem tps harness to a factory fix that involved some upgraded wiring harness...

Worst case scenario...if it is the TPS, I guess I can swap in the high altitude model I've had laying around for a while...

Thanks

old_man · Apr 30, 2004

High altitude TPS????? There is a high altitude CPS, but I've never heard of a high altitude TPS. The CPS is mounted on the bell housing, the TPS is mounted on the throttle body.

Which one is it?

Gil BullyKatz · Apr 30, 2004

Just got home from another test run...

Everything seems ok now...

And yes I did have too long a day today... You guys are right about the TPS being the possible culprit... Not the CPS... I got my acronyms all screwed up... The TPS makes complete sense

Think I'll save the Hi-alt CPS for the stroker and slab some di-electric grease on the TPS connectors...

Thanks y'all

RINGKONG · Apr 30, 2004

Gil BullyKatz said:
Just got home from another test run...

Everything seems ok now...

And yes I did have too long a day today... You guys are right about the TPS being the possible culprit... Not the CPS... I got my acronyms all screwed up... The TPS makes complete sense

Think I'll save the Hi-alt CPS for the stroker and slab some di-electric grease on the TPS connectors...

Thanks y'all

your welcome..

Auto trans not shifting.....

Gil BullyKatz

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RINGKONG

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Gil BullyKatz

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XJTripp

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bbell90xj

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old_man

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Gil BullyKatz

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Gil BullyKatz

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