i recently picked up an 88 cherokee that will not shift out of first gear. I was wondering if this was a common issue and if some one could point me in the right direction towards getting this fixed. It goes into to drive and reverse fine but will not up shift even if I try to manual shift it will not do it.

 

What tranny?

 

Sounds like the TPS,but don't know it that yr. has one.

 

Assuming automatic here?

1. Be sure fluid is at the correct LEVEL on the dipstick, is RED in color, and does not smell BURNT

2. Test AND adjust your throttle position sensor. Absolutely critical sensor for transmission shifting performance. More on that below.

3. Be sure your TV cable is adjusted properly. Here is a link to that thread.

https://www.cherokeeforum.com/f2/free-quick-fix-41821/

Hope this helps; good luck and be sure to check back and let us know what you find!

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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. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, 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 has 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.

 

ok I am outside messing with it today. I noticed the tb cable was not hooked up. that was an easy fix but it did not fix my problem. I went to check the throttle position sensor and noticed that in the passenger floor board there was a TP sensor laying there. I checked all my connections and broke out the fluke and everything seemed ok. I did notice when i test drove it, that there was no speedo! I am starting to think speed sensor now. If anyone knows a different direction to head in let me know

 

Speedo is cable driven in 1988.

Did you test the TPS per the instructions Mr Walker posted, and on the "trans" side?

 

ok here is an update. I had to put the jeep on the back burner for a while. today I went out side and unplugged the tcm. it will shift through the gears as long as I manually shift it. So I think one of the input devices to the tcm is acting up. now I just have to figure out which one.

 

Throttle position fails way more often than the TCU.

That is still a primary suspect. Test or replace.

 

See Post #4.