bad tps?

I have a '88 Jeep Wagoneer Limited 4.0L. Recently, I've been having troubles with the transmission. When you are above 30 mph and you take your foot off the gas enough so that it upshifts, the transmission has a hard time deciding whether to stay locked up(torque converter) or not. This results is a harsh jerking motion until you take your foot off the gas completely or give it more gas. Also, if you put the transmission in power mode, it doesn't do this as much. So I'm thinking it is the tps because I was able to adjust the tps so that it wouldn't do this. However, after a month of this happening every week, I can't adjust the tps to get it to shift correctly. Is it the tps or something else?

Yes, the most likely suspect is the TPS. Also check the ground to the TPS, these can become flakey, causing shifting problems.

Did you adjust the TPS randomly or via an established procedure? It's not difficult to test the TPS. You can check it with a volt meter to see if the voltage varies smoothly as you open the throttle. Seems like a lot of folks like to replace them on suspicion without determining if the thing is truly faulty.

PaulJ said:

Did you adjust the TPS randomly or via an established procedure? It's not difficult to test the TPS. You can check it with a volt meter to see if the voltage varies smoothly as you open the throttle. Seems like a lot of folks like to replace them on suspicion without determining if the thing is truly faulty.

Click to expand...

I adjusted it following the guidlines in the Renix manual.

This may see off the wall but have your EGR valve checked out. They can get dirty and stick. I had a surging problem at 70 mph but if I backed it off to 60 it went away. I took it in and the mechanic figured out it was a sticking EGR.

A buddy of mine said to me after I got it fixed "that confirms my thinking that problems like that are not transmission but engine. You'd think transmission but it is the engine which supplies the power".

Also you talk about it wanting to go into and out of lock up. Are you driving on level ground when this happens or you going up and down "hills"?

Also there were a TSB on the TPS and it gave new setting procedures. If possible get a garage to hook up the test set to it and set the TPS that way. If you do it with the test set then you eliminate any DC voltage drop in the chassis harness. I used the multimeter method and then I had the XJ in the shop. The tech told me "I adjusted your TPS it was out of spec".

I'm thinking it is a MAP Sensor problem because I had it disconnected for a while before this started to happen. It also feels like the engine is the problem and not the tranny the more I drive it. However, the EGR valve hasn't worked in over a year.