2005 LR3 V8. When driving at low speeds my engine speed will fluctuate about from 2-500 RPMs very quickly, almost like how a vehicle with an idle control valve can "hunt" for a stable idle. it's annoying as ****, because you can be going down the road, with your foot giving a certain amount of pressure on the throttle, then the speed jumps 500 RPM higher, and you have to back off the throttle a little.

Scanned for codes already, no dice. Tried resetting the vehicle with +/- battery cables touching, already reset trans adaptations, and installed a brand-new battery. I'm thinking throttle position sensor on the pedal, or a bad throttle body?

 

You can google the reset procedure for the throttle position sensor. Something along the lines of turn ignition to pos 1 or 2, hold down pedal for 45 seconds, turn off ignition and release pedal. I don't recall it exactly.

Otherwise I'd be leaning towards throttle body. Not a cheap part unfortunately but user replaceable. Mine did the same thing, never fixed it though.

 

Try cleaning the throttle body. Buildup around the throttle plate can make it difficult for the engine computer to operate the throttle. The computer adapts to this type of buildup, but if those adaptations are lost for whatever reason (ECM programming, battery disconnect, etc...), these adaptations are lost and the computer hunts.