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
Serial number? Are you saying the engine idles and does not rev up more than an additional 100 - 400 rpm, or are the rpm's fluctuating when at fast idle?
Rpms fluctuate from low idle to 3/4 throttle, we don't ever run wide open... It's digging every day, hard to do fine work when its acting up... Serial FF120CX034560
Sounds like air infiltration or vacuum on the system. Try removing the fuel tank cap to see if it improves. Try to get a fuel pressure reading at the filter head and post results.