Deere 120C Engine Throttle Problem?

Throttle has been throttling up about 100 r's lately its been getting worse my best guess its some times rev up 400 or more r's... have changed the throttle dial and check to see if the A/A A/I dial is ok.... we wiggled the wires going in the the injection pump also, but no luck finding the fault yet. no engine codes... we even hooked up our DR.EX