Its got 100,000 miles on it and its stock. Not much in the way of problems the first 10 years/100,000 miles.

This weekend the engine revved up on starting to about 2000 rpm and gradually worked its way back to normal twice. Sunday, out on I64 it was in cruise control when I tapped the break to slow down. There was a clunking/bumping noise and the check engine light came on. No gauge issues so I kept driving. It would not go back into cruise control (light is on but no cruise control). Finished getting home and had a couple of very short clunking/bumping noises a few miles apart.

Put the code reader on it Monday - code 0121 and 0123. I got a new throttle position sensor Tuesday and installed it. The code 0121 and code 0123 erased but now I have a code 0122 (didn't have that with the old TPS).

I drove it to work this morning and noticed the torque convertor is not locking up either. No cruise and no torque converter lock up - sounds to me (but I'm a very inexperienced Jeep back yard mechanic) like there is something "telling" the Jeep that the brake is still on - hence no cruise control or torque converter lock up. The brake light is not on and I've pulled up on the brake pedal to see if it was sticking/dragging but no luck getting cruise or torque converter lockup. Any suggestions on what to check next? Thanks.

As to the code 0122 - also had an unusual shifting problem at one of the many stop lights on the way home. It acted like it was not shifting out of second gear (3200 rpm at 45 mph rather than the usual 1800 or so) but at the next stop light it started shifting normally again.

I've read TPS issues can affect transmission shifting. I sure hope that is all that is wrong with it.

Is it possible the new TPS is bad, too? Should I take it back and ask for another one?

I'm going to have to find some good shop manuals for this thing as I plan to keep it.

 

Check this thread for code 122, seems like it may have been a hold over from the TPS replacement.

http://www.jeepforum.com/forum/f9/er...-p0122-503282/

 

I'm not driving it again till I figure this out. The torque converter not locking up is an issue but not a show stopper. However, that one instance of not shifting correctly (over 4000 rpm from second to third and then not shifting into overdrive) has me worried. I could smell something getting hot from one stop light to the next (it was turning about 3200 rpm for a couple of miles).

I just ordered a 5 book set of shop repair manuals (shop manual, and four diagnostic manuals - body, transmission, powertrain and chassis). We'll see what's in the books when I get them next week.

Its too nice a vehicle to tear up by chancing driving it with whatever is going on with the TPS and the shifting.

 

Well, no resolution yet. The manuals should be here any day I hope.

I keep learning more but I'm not sure what it means.

1. After I replaced the old TPS the original codes could be erased with my code reader. Now I have the new/different code P0122.
2. If I try to erase it the light will go out during the erase step but will come right back on again.
3. When I start it up it will rev up to about 1200 to 1300 rpm. If I then turn on the AC the rpm will go up to 2100 rpm and then drop back down to 1200/1300 when I turn the AC off - this was not happening with the old/original TPS sensor and the original codes (PO121 and PO123).
4. A few years back my youngest son had put a cable tie around the linkage to space the throttle linkage up off the adjustment screw that passes through the throttle body base (that you can't get to without taking the throttle body off the intake) for some reason that neither son can remember. If I put it back in place to provide that little change in angle for the throttle plate in the rest position the P0121 code will erase and not come back - until you start the engine up.

Come on shop manuals....

 

Well, it appears to be fixed. Erased the codes, took it for a drive, the cruise control worked, the lock up torque converter worked, no more check engine light. Going for another drive this evening.

I made a mistake while troubleshooting that led to more issues. They were resolved today when I got my newly purchased shop manuals out and went through the TPS wiring diagrams.

The mistake? While trying to check the voltage on the high and low sides I had to take the plug apart to get to the wiring due to the way the plugs are sealed up. Yeah, I could check the voltage with the connector unplugged but not when it was plugged into the TPS. So I took the wires out of the plug, put them on the TPS one by one and then checked them. When I put them back in the plug I reversed the input and ground wires in the connector. That's why the code changed from the 121 and 123 to a 122 - even with the new TPS.

I cleaned the throttle body good with carb. cleaner (probably fixed the problem but by then I'd already reversed those two wires). I installed a new TPS (after I'd reversed the wires).

I put the old TPS back on and still had the code 122.

Today, after getting those two wires in the right spot in the plug the code erased and it ran great even with the old TPS in there - which is why I said cleaning the throttle body up may have been all that was needed.