New liberty owner

[Redx]

Okay, I have a few problems with my 2004 Jeep Liberty. It has a 3.7L 4x4. Aproximatly 200k miles on it. One issue I've had since I've received it is that noticed when I'm just sitting it will rev up a little, but it will also do that whIle I'm driving! Cruise control on or off it does this, I can feel it, and on the rpm gauge I see it go up them back down, up and back down. I have no idea what this could be! Now just last Saturday my cruise control decided to stop working. Sometimes I can get it to turn on and work but only for a few miles and then it kicks it off. Then it does not want to turn back on!

 

[Conundrum2006]

Um, my guess would be something like TPS. Throttle position sensor. Just a guess.

In my 3.7 Commander which I just got running again it seems like cruise control turns itself off if I accelerate to pass a car and let it slow down on it's own (no idea if it supposed to probably ought to check the owners manual). This is why I think TPS with the odd rmp revs and losing cruise.

EDIT: I may be all wrong. According to my owners manual cruise control should go back after acceleration. Have to test mine again.

Other guess would be brake light switch. (Sometimes tapping the brake will cause the torque converter to disengage and rmp to fluctuate)

 

[LibertyTC]

If the rpms are surging it could be the TPS but also the IAC controls idle and it needs to be clean. I recently replaced both IAC & TPS.
Clean the throttle body and ensure the butterfly (plate) door and barrel is clean, free moving plate.
IAC see post 10: http://www.jeepkj.com/forum/f196/idle-air-control-no-screws-44826/
For TPS see this link: http://www.jeepkj.com/forum/f196/throttle-positiion-sensor-replaced-tps-59336/

 

[Redx]

Thank you! When I go home tonight I'll look at it, clean it and look at it. As well as another problem I forgot to mention.
Sometimes not all the time, it seems to switch to 3rd gear (not sure if it is third) but it seems to get stuck in 1 gear and stay there, I'll have a slow take off, and it will not shift and my rpms get to like 4 rpm at like 45 and won't shift. It happens even if I'm going about 20 miles an hour,and I have to turn the car off and turn it back on to get it to run normal, but it does it again sometimes. As well as it seems to shift later and harder than usual ever since my cruise control has stopped working

 

[Conundrum2006]

Have you check the fluid level?

That's a puzzler. Seems like it could be electronic since it can be restarted and run normally but I'll step out of the way and let someone who knows this transmission tell you what to look for.

 

[JasonJ]

Sounds like transmission slippage to me. Check the fluid condition and level, hot, on flat level ground.

Consider trans fluid and filter replacement if it has not been done recently.