About once every 20 minutes while cruising at 60-80mph, my 99 XJ will lurch forward. It almost feels like the car shifts down and back up again very quickly making the car “buck.”

I tried replacing the TPS but it didn’t help. It’s not throwing a code so I’m not really sure what else to try.

Any ideas?

 

I had similar symptoms as you. I replaced my Crank Position Sensor and the "bucking" stopped. I replaced with a MOPAR sensor.

 

Sounds good, I think I'll give that a try. Just curious, was your check engine light on before you replaced it? Just worried that mine might have some sort of mechanical issue in the transmission that isn't throwing a code.

 

No, don't give it a try. Test it. (see below)

Throwing parts at it because "well, that's what fixed some other guy's problem" is a very expensive, frustrating, and stupid way to fix a car.

Does your RPM suddenly change when this happens? It's possible your torque converter is unlocking.

 

just as a fyi...I had a very similar issue. It ended up being the cam sensor... problem is that is was an aftermarket dizzie and couldn't get a sensor that wouldn't "tick"....I ended up replacing the who dizzie with a new one...no problems since.

 

No, my check engine light was not on at the time nor did it illuminate after one of the "misses" or "bucks".

 

Yesterday as I was accelerating onto the highway I lost pretty much all engine power and the RPMs dropped super low. I took my foot of the pedal and rode the shoulder for a few seconds, after that I gave it some more gas and I was able to get up to speed like nothing ever happened.

Does this make the case for a bad CPS a little stronger? From what I've read RPM drop and loss of power is a pretty common symptom.

Unfortunately I don't have a continuity tester so I can't be sure.

e: Just for clarity the RPM drop is a new issue, previously there was just a small "bump" that felt like a quick down/upshift with no significant change in RPM.

 

I had something like that happen. It was self inflicted by me not tightening correctly an electrical connection at the PDC box. Anyway, there are some important connections/electrical stuff that can cause your symptoms. I found my issue by wiggling the wires in the engine bay with the Jeep running. When I wiggled the offending wire, the Jeep shut down. I would start with the battery wires, clamps and grounds. Then inspect the PDC wires. Look for bad wires, loose connections and such