My jeep at first started acting up feeling like the tranny was slipping but later i came to find out it was just down shifting when i was crusing or accerlerating. it got worse untill it eventaully wouldnt shift out of first gear at all, so i had 1st park and revers. so i desided lets change the tranny. didnt fix my problem, then i did some reserch and discoverd that it could be the TCU so i unplugged that and it worked i could shift it manualy. so when i got around to getting a new computer i put it in, and get this "The problem wasnt as bad, it just felt like the tranny was slipping a little, but it did shift. the problem wasnt fixxed, i put the old computer back in and it wouldnt shift at all just stayed in first."Two diferent computers and same problem but one not nearly as bad as the other??
Next i found out it could be the TPS so i changed that, "heres where it gets intersting" worked for a couple days then started acting up, changed it again thinking maybe it just went bad, samething a couple days went by then it started acting up. "So, by unplugging the TCU and it shifts fine manualy means that theres no dought it has to either be the TCU or the TPS but i changed one then the other and then both, but it only works for a couple days then acts up?" what els could it possibly be?
i thought because i got a diferent TCU and i still had the original tps "which was fried in the end when i tested it" and the problem was les savier that it was a my TCU plus my TPS that was bad, but the TPS was bad and i changed it but yet the prolem continues.

I really need help with this guys, anything you got to give is helpfull thanks!

 

I would "test" the new TPS to be sure. This does sound electrical to be sure. I would spray clean the connectors for both the TCU and the TPS with some electrical contact cleaner (available anywhere, even Walmart).

Also, be sure that your TPS is adjusted, the 87-90 TPS requires adjustment. More below.

Keep us posted.
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RENIX TPS
(Thanks to Joe Peters from NAXJA for this information)

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. Wire "A" is positive. Wire "D" is ground. Remove the three-wire connector from the TPS. Key ON, measure voltage from "A" positive to "D" ground. Note the voltage reading--this is your REFERENCE voltage. Now, reconnect the three-wire connector to the TPS. Key ON, back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. 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 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 four-wire connector. For the automatic transmission equipped vehicles the four-wire connector provides data to the TCU. Disconnect the four-wire connector. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Now, reconnect the four-wire connector to the TPS. 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. 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.

 

theres so many different things ive tried its for sure not the tps or the tcu, i have changed the TPS 3 times now. but your saying maybe the conectors arent making good conection?

 

Im pretty sure there is something going on thats ruening the TPS sensor I just have no clue what

 

It is unlikely that something is actually ruining the throttle position sensors.

The reason I recommend cleaning the connectors is that if you have a dirty connector, you have a good source for intermittent problems. And inspect the connectors closely as well for damage to any of the contacts.

Dielectric grease in these engine management sensor connectors can also help with ensuring good signal integrity through that connector.

 

since you checked all the obvious symptoms, the only other thing i can think of is the inline fuse that's in the wire harness about 5 inches away from the TCU plug connector.

otherwise

 

whats the year of your cherokee?

 

I would check the linkage on the throttle body and make sure there is no play in the trans wire and engine throttle linkage. You can adjust the linkage for the trans by turning the little plastic spinner around the bike wire looking thing. Make sure the 2 pull at the same time.

 

Its an 89

 

i would think that it might be the wire too, except he said it shifted fine when he changed the TPS and/or unplugged the TCU. i would say that you have a bad ground to the TCU, hence y the other one died. a bad ground will cause voltage to be off hence shifting wrong, and killing the unit. so i say check the ground to the TCU

 

yeah sounds like a bad ground or a bad connection. I would look at the harneess that runs beside the valve cover and take a look at the big black connector on the driver side firewall above your master cylinder that connector is known to get dirt and water in it

 

i have no clue where the ground would be but, ill take a look

 

now that you mention that, right before this problem came up, i did do some speaker wiring to the battery through the fire wall on the drivers side, i guess i could have bumped something, or screwed something up doing that.