Jumpy RPMs at around 50-55 MPH?

Hey,
when driving between 50-55 MPH, my RPMs get jumpy and it's really wierd. If I don't either let off the gas and give it gas, it jumps from say 1750 rpms to 2250 rpms back and forth. Less than two second to go up and down. Is my XJ switching back and forth between 3rd and OD? Like it gives it enough juice and jumps to OD, then it doesn't need it and drops back down, and back and forth? Hopefully this makes sense

- Kevin

What year? It sounds like the torque converter is locking and unlocking. You should check the TPS adjustment.

Mine was doing the exact same thing for a while.(Ive got the AW4 tranny) and I replaced the TPS and now it doesnt. Hope that might help.

Why I always forget to include pertinent info I don't know It's a 1990 with a I6. As for checking it, all I have is a Haynes guide, it says to check it with a voltmeter, is that how I would go about doing it? As well, is my O2 Sensor the thing in my exhaust pipe between the cat and the exhaust manifold?

Thanks,
Kevin

Mine occasionaly, goes chunk chunk chunk (torque converter locking and unlocking),at almost exactly 2000 RPM. I adjusted the TPS, which helped, but didn´t cure the problem. I´m gonna replace the TPS. Mine also has some, out of specified, voltages going into and out of the TPS, this could also be a factor. I´ve got a used TPS, around someplace, I´m gonna try before I shell out the bucks for a new one. Like I mentioned, it could be in the wiring and/or the TCU.