JeepFan

Help! I am having 3 weird auto trans problems...

I have a 1990 XJ with 116K original miles. It is bone stock except for a 4" lift and Borla exhaust.

A few months ago, I had a vacuum leak which caused a gunk build-up in the engine. I fixed the leak, removed the valve cover, cleaned the valve train, and ran some gunk remover through the engine. Everything worked great except for the transmission would no longer downshift from overdrive at full throttle.

I did the transmission shifting adjustment at the throttle body, but it didn't help and I just lived with it.

Now, it has started doing something even weirder...

I will be cruising along on the highway (55 mph) and it will seem like it is shifting down for a couple of seconds. My RPMs will jump up a couple hundred RPMs for a second or two, and then go back to where it was. It does this for no apparent reason as I might be on a level highway and holding the throttle steady.

Finally, it also seems to shift backwards sometimes. It will be in one gear, and when I go up a slight hill on the road and need more power, it will shift up!

Although this is my 9th Jeep, I will readily admit that I know absolutely NOTHING about auto transmissions. But, I would swear that this thing has 5 or 6 gears - although I know that is wrong. Any advice or suggestions would be EXTREMELY helpful and appreciated.

TrekkerJmm

Hi and welcome to CF from Tj... Could be the throttle position sensor going bad or the torque converter locking and unlocking...Tj

96_xj

welcome to the site!

try a simple 30 second FREE fix first. that is to adjust your throttle kickdown cable. (again)

and then look into what was posted above your TPS and torque converter

JeepFan

Thanks for the welcome and the advice. I tried adjusting the kickdown cable again with no new results. I'll try replacing the TPS next.

Quick question: Are there any vacuum advances or anything for the transmission? The reason I ask is, when I had that previous problem with the vacuum leak and the gunk build-up, I never cleaned or replaced the vacuum lines. Maybe one or more of them is clogged?

JeepFan

It worked!!!

I replaced the throttle position sensor this morning and now my auto trans is working perfectly. I did not realize that the TPS was also connected to the tranny. Thanks for the GREAT advice. I never would have thought of it.

90xj,99xj,92mj

ya they are a pain. . my jeep would not shift out of first but when i replaced the tps it worked like new. damn sensors ha

96 XJ 4.0 Auto

Mine is shifting at exactly 3,000RPM maximum (less if driving slowly)and will NOT kick down. Otherwise seems to run fine. I expected to get a check engine light if it was a bad Throttle Position Sensor...
I'm leaning that way because the cable wouldn't make it shift at 3,000RPM.
Am I on the right track?