rpm fluctuation while driving
 

As I am driving between 30-50ish mph...the engines surges or rpms fluctuate badly. Problem has existed for quit some time...never happens at idle. I have changed alternator, always clean tb and maf. Any help?

05 lr3 v6

APP sensor (gas pedal position sensor) would be one thing to check. Tells ECU where to dial up the electronic throttle. See attached.

Thanks Savannah Buzz...I will troubleshoot that. Have heard could be transmission, although it doesn't feel like it is slipping out of gear or anything, and also heard torque converter is bad and can be rebuilt. Lots of things to check....will start with the easy stuff. Already did fuel injection service, new plugs etc. Haven't done new wires though, and i have 164k miles! Been a great vehicle entire time.

I do not mean to resurrect an old thread but I have the same issue as the OP.
What was the fix?

Thanks

Torque converter. At least that's what my mechanic said (he's a Rover specialist, not the dealer). I definitely agreed that was it. I have done tons of research. I checked out all the easy stuff first of course. Scheduled appointment at a local zf transmission shop to drop tranny and rebuild torque converter. But it was totaled before we took it in via wreck.

Sire. No fix as of yet. Going to try to reset the TCM soon.

Just reset the TCM with the iLand tool (made by Atlantic British). Shifted much differently than it has for the last few years. No more RPM fluctuation as the transmission seemed to automatically and quickly shift between 3rd and 4th while traveling on a flat road at around 35MPH. Very minor kick just before coming to a complete stop a few times. Drove for about 20 minutes in town. Then, just as it properly downshifted while driving down a hill, it displayed a "Transmission Fault Code Only Limited Gears Available" and an "F" appeared where it normally displays "D". Made it home it what seemed to be 3rd gear. Turned off the car. Turned it back on and fault code was gone. Will take it for another drive tomorrow.

All of this indicates that the RPM fluctuation was being caused by the transmission control module all these years (and approximately 110,000) miles. Seems to rule out the torque converter. Will update tomorrow.

After resetting the TCM for a second time, I'm no longer getting the transmission fault code even after two long drives. However, still occasionally experiencing a small "kick" just before coming to a complete stop (feels like being rear ended by a little car traveling at just a few MPH). When I described that to Garrett at Atlantic British, he advised me to take it to a dealer to have the ECM and TCM software upgraded/updated with the Auto Logic diagnostic tool to solve the problem once and for all as the new software has broader parameters which eliminate both problems permanently.

Thanks Savannah. After three years and investing several thousand dollars into other potential fixes - your suggestion solved the problem. No more RPM fluctuation. It's gone. Fixed! I cannot believe that replacing the gas pedal assembly (which includes a new APP sensor / gas pedal position sensor) finally solved the problem. Thank you so much!

Good to hear I might have to give that a try as I have a similar fluctuation