I have a 93 D250 with the Cummins. Just had the Injector Pump replaced 50-100 miles ago. ($1700). Yesterday my idle went high. Around 1500RPM. It is steady (1500) at Idle and when I come to a light I have to fight the truck to slow down. I am worried about driving it as I don't want to slam it into gear when it is idling that high. Had it towed home.

Where should I start with the troubleshooting? I have a small fuel leak at the fuel filter and will be buying a new one today. All the linkage is tight. I have not touched the engine since the pump install.

 

who did the pump install? is the throttle linkage moving as it should and not stopping anywhere or holding the throttle open? there is a throttle adjustment but from my experience it is pretty tricky to get at and probably shouldn't cause a huge difference in idle speed.

 

Took the truck to a shop that specialized in older Cummins. The linkage is perfect.
If it were a gas engine I would say the choke is stuck open. It idles nice and smooth at about 1500 instead of 750. When driving and slowing I have to hammer the brakes and she tries to keep going.

 

sounds like you need to be talking to the shop that did the work. they must have done something wrong