I have a 93 Cummins that is starts fine, but has a extremely bad lopping going on at idle. The lopping sounds so bad that it sounds like its going to die. If I give it some pedal it will stop the lope but still runs really rough, has some smoke but doesn't look really black or really white either. Already checked the fuel filter, seems to have good pressure to the injectors, have bled the lines of any air several times, and it's still has not changed at all.

So anyone have any ideas of what could be wrong with this?

 

Start it up crack the injectors one by one see if it changes i know you said u bled them but it takes a while to get the air out if it starts fine it couldnt have jumped time. How far will it rev b4 it cuts out of loping?

 

Just a little rev will get it to stop, maybe 100 to 200 more rpm and it will run bet it is still rough and thats when it will start to smoke when you pedal it. we started it with the bypass rail unhooked and nothin was comin out except from the end where it feeds back to the tank.