I'am just about to give up this XJ if I cant figure out this issue. At 35-40 mph cruising the RPM will move up about 250 RPM and go back down as if it just shifted down and shifted up again. This only happens at this speed range and it idles perfect.

So far i have replaced all ignition components (cap, wires, rotor, plugs, coil), Mopar TPS, and have adjusted the Transmission Kick Down cable, and new 02 sensors, new battery.

Background info, 97 Sport 2 door auto with 200k miles, no codes.

Anyone have any ideas whats going on?

 

That is the exact speed my torque converter locks up and unlocks, maybe there is a problem with yours, it would make the rpms jump up and down like that if it is locking and unlocking repeatedly.

 

"Anyone have any ideas whats going on?"

You like to buy & replace parts?

 

Bingo!

 

Is this normal then? This is my first XJ so I'm not sure if I should be concerned.

 

All the parts needed to be replaced. I inherited a very neglected jeep from a brother that never took care of it.

 

If is it doing it rapidly then there might be a problem with it, if it is every few minutes as you drive and your speed changes maybe not. Mine will lock at 40 then unlock just above 35, but it should not go in and out when the speed is steady.

do remember some of the first locking TCs back in the early 80s in GMs that would kick in and our really fast and make the whole vehicle shudder, but newer ones should not have that problem.

 

Great! thanks for your help I think I am just noticing it more as I drive and it happens every once in awhile around the speed of locking and unlocking. Im coming from a 5 speed manual and I haven't driven an automatic for an extended period of time to notice the unlock and locking of the torque converter.

 

Same with me, I noticed it since I recently bought my XJ, my F150 is a 5 speed that I have driven for the last 17 years, still getting used to the auto again.