97 cummins with Banks installed. Always ran great until setting for 6 weeks. Now it starts fine but when you stop giving it fuel it will not idle back down. It will stay about 1200 rpms. If you tap the accelerator quickly or restart the engine it will idle fine. The truck runs fine other wise.

 

You need to check your linkage for binding. Either that or your IP is beginning to fail you. Meaning a plunger might be sticking.

 

I believe there was a TSB for throttle linkage replacement:

http://dodgeram.info/tsb/1997/18-29-97.htm


But the problem does sound a bit more like pump issues.

 

check the linkage rod up on the pump for slack, the rod has poly bushings and can be replaced for about 5 bucks from the cummins house,