I have a 1989 automatic and iv been having some
Problems with the transmission it shifts slow and sometimes get stuck in 3rd gear when in drive no matter how much I floor it still won't upshift downshifts are fine any ideas what it could be? Also when I get on the gas a little bit it tends to rev out and take at least over a second to shift like a lag or delay any help would be greatly appreciated.

 

How does your fluid look? Is it bright red or is it dirty? Does it smell burnt? It could also be your TPS. Luckily you have a Renix do you can adjust your TPS if needed. I don't remember off the top of my head what the voltages should read. I'm sure one of the Renix experts will chime in.

 

Check your TPS on the "trans" side using a voltmeter.

 

Had this problem with my 88. It's your TPS.

 

Here's how to adjust the TPS after you replace it:

RENIX TPS ADJUSTMENT
Before attempting to adjust your TPS be sure the throttle body has been recently cleaned.
It's especially important that the edges of the throttle butterfly are free of any carbon build-up.
IMPORTANT NOTE: Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector
of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post.
If you see more than 1 ohm of resistance some modifications to the sensor ground harness will be
necessary. The harness repair must be performed before proceeding.
I can provide an instruction sheet for that if needed.
MANUAL TRANSMISSION:
RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body.
This manual transmission vehicle TPS provides data input to the ECU. The manual transmission
TPS has three wires in the connector and they're clearly embossed with the letters A,B, and C.
Wire "A" is positive.
Wire "B" is ground.
Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors..
Note the voltage reading--this is your REFERENCE voltage.
Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your
OUTPUT voltage.
Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For
example: 4.82 volts X .17=.82 volts. Adjust the TPS until you have achieved this percentage. If
you can't achieve the correct output voltage replace the TPS and start over.
AUTOMATIC TRANSMISSION:
RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-
wire connector, same as the manual transmission vehicles have, and it is tested the same as the
manual transmission equipped vehicles--FOR ENGINE MANAGEMENT RELATED ISSUES.
However, the automatic TPS also has a square four-wire connector clearly embossed with the letters
A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module.
Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your
REFERENCE voltage.
Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT
voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage.
For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage.
If you can't, replace the TPS and start over.
So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and
the other side feeds the TCU. If you have TRANSMISSION issues check the four-wire
connector side of the TPS. If you have ENGINE issues check the three-wire connector side of
the TPS.
For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is
stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.
Revised 11-28-2011

 

I have the same problem in a 1996 do I have to replace the transmission only 121000 miles

 

I adjusted his tps a while ago to remedy the high idle start problem. The trans side is less then .83x reference voltage but I can't remember what it is. Maybe .79 or somewhere around there. Its kind of crappy that the trans and engine outputs are combined on these engines. I've seen the high idle issue so many times with the tps properly adjusted. From what I've heard that is the flaw inherent to this integrated design. My tps is adjusted to .78 to get my idle correct, this is on a new tps.

 

My '96 was acting up like this. Replaced the TPS and it's a complete change. Seemed like a new transmission.

 

My 1989 will not shift at all. Unless I redline it. The fluid smells burned sometimes, but its clean fluid. Sorry I wasn't trying to thread jack.

 

Tps sensor possibly

 

Test your TPS on the "trans" side.

 

One of the problems with the high idle is the ground for the engine side of the TPS is not good. That's why I advocate checking that ground circuit in the beginning of the instructions.

 

You and I went through that. Mine still had high idle till I fudged the numbers on the adjustment a little.... It was a while ago. My aw4 shifts great though.

 

I've slept since then.

 

Ya. It's been a while. I prob haven't been on in 3 months