AVjeeper

For the past week I've noticed that when I take my foot off the accelerator and coast for a red light and my speed slows to about 25mph the tranny downshifts rather hard. It almost feels like a manual tranny downshifting. It's never done anything like this the last 15yrs.
Anyone have any ideas?

Much obliged,

tjwalker

Test and adjust your "throttle position sensor". It is directly involved with transmission shifting characteristics. Could also verify adjustment of your TV cable.

Here is a link to the adjustment procedure of the cable and also more on verifying the TPS. Good luck!

http://naxja.org/forum/showthread.php?t=1015963

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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.

AVjeeper

Thank you for such a detailed reply. I actually thought it might be the TPS at first. This is what actually happened. The transmission fuse was burnt out. I noticed that the light on my Trans Power rocker switch was out. Last week I added some backup lights on the trailer hitch. I spliced into the stock backup lights. When I did I connected all the red wires together, but I grounded the new lights to the body. Somehow this was causing a short. I just spliced all the black wires together. The backup lights all work, the tranny is shifting right and the fuse is not blowing. I don't really understand all this though. I was very surprised that the tranny fuse is tied into the backup lights.
Much obliged,
Jason