i have a 05 cummins that when it starts up idles fine, if you go to rev it up a lil in park or neutral tap the gas or run it up to a certain rpm and leave off the gas it stays at what ever rpm you left the throttle off at,in hand if you were holding the truck at 1500rpm and left off it would stay at 1500 rpm, if you tap the gas and it goes to 2000rpm it would stay there till you shut it off and restart it then it would idle again till you touch the pedal, with the scanner hooked up the throttle% goes up and down with the pedal along with the ohms to it, it has no check engine light and only dos it in neutral or park, any input ,posted on another sight got very lil input , dont want to replace injectors or other expensive parts if it is just a lil part, any help would be greatly appreciated

 

You've ruled out the APPS (I think the 3rd gen autos still had them?)...

 

If the APPS checks out, start working on injector tests. Check for diesel in the oil, check injector return flow, pull the VC and ohm out the harness and the injectors, check cylinder contribution on a scanner. That should start to build a picture of potential problems.

FYI, dose it hard with additves like power service and run 2-stroke oil thru it. The FCA can get sticky and cause things to go off kilter. Make sure your batteries are good and all the connections clean. ANY potential noise in the system will cause weird behaviour.

Last but not least, pray and say several dozen Hail Mary's.


Good luck.