So just today I noticed my jeep will start bucking when crusing at about 60 mph...about once every 2 seconds for a short period of time. Its as if the transmission is trying to upshift but it never actually does. It is entirely random at the moment and it sometimes happens under acceleration. The RPMs drop sharply by about 250-300 then sharply bounce back up. Letting off the gas fixes it usually. Sometimes however I can go quite a while with no problems whatsoever. It Idles fine and I have no CEL. I had the TPS come unplugged on me before and give me similar issues but in this case the engine never sputters or acts like it will die. My first thought was something with the TCM or possibly the torque converter lockup but I am unable to get the symptoms to show themselves on command. Its hard to explain this because I've never experienced this sort of thing before...

 

Look up above at the top of the brake pedal. Maybe the brake switch is not adjusted properly.

 

To explain the above, the brake light switch may be signalling intermittent braking which will disengage the TC lock-up, which raises the RPM by 250-300.

You can replicate this by very lightly tapping the brake pedal when at speed, not enough to actually brake, and you should see the RPM increase.

 

Ok so update...the engine has actually started sputtering, still no check engine light but that rules out transmission. It is a much harder jolt than just giving the brakes a tap or coming out of lockup so its definitely loosing power then regaining it while in lockup

 

Ok so update...the engine has actually started sputtering, still no check engine light but that rules out transmission. It is a much harder jolt than just giving the brakes a tap or coming out of lockup so its definitely loosing power then regaining it while in lockup

 

I had the same intermittent problem. It ended up being the PCM after trying to chase it down, one morning, she would turn over, but not start.
the thread is here,, https://www.cherokeeforum.com/f2/sen...roblem-251669/

 

I can't help but wonder how many PCMs have been changed because of a bad connection on one of the plug pins, not the unit itself. Just the fact of unplugging it and plugging it in again can clean off corrosion that's invisible to see, especially since most sensor signals are only 5v. Considering the environment they work in and the fact that the connectors are not that air tight, the first thing I would do is clean up all the contacts before I condemned the PCM.

 

did that.....