All,

My sister has an 89XJ with 289,000mi with an auto tranny. She brought it up to my house so I can change her blown valve cover gasket and she is telling me when she is driving in town and she starts from a complete stop, her XJ will not shift normally. She described the XJ to stay in first gear and will only shift into second gear until she gets her speed up at a much higher than normal speed. If she is at full throttle, it will shift as expected. It is only at lower speeds, under light throttle or from a stop that it is not shifting correctly. If you attempt to speed up from a start and then slow, the tranny appears to go into neutral. Something with the shift points is not correct. Her tranny fluid level and fluid condition is fine. My best guess is a vaccuum issue or valve body issue. Mabey even her torque converter. The tranny is not slipping, it just will not shift correctly under light throttle. Any help would be much appreciated.

Thanks

 

It's the throttle position sensor. You'll notice there are 2 harnesses on the TPS. One is for the fuel system and the other is for the transmission. My 89 did the same thing. Would only shift when you redlined the engine.

 

can she shift it manually fine?

 

i think i have something similar to that, anytime i stop faster than grandma my tranny shifts into what i think is neutral, then will go back in by itself. it has 226k miles, and i think it has never been serviced, i recently refilled the tranny fluid but idk what to try next.

 

bad throttle position sensor

 

the tps is next to the iac on the throttle body right? i tried everything to get it off and got to the point where i was using a dremel to cut the heads off the bolts but chickend out. what should i do? cut it off and buy a new one?

 

If you just cut the heads of the bolts off you should be able to grab whats left with a pair of vicegrips. On the 89 the TPS is on the front of the throttle body. It should be held in place with two torx head screws/bolts.

 

i think im just going to junkyard to source a whole throttle body so i can port it and get a new tps on it at the same time

 

Yeah that's one way to do it. I was lucky with mine. The TPS screws came right out without a fight.