Hi, I'm having a problem with a rough running engine. It rocks at idle in gear or out and has a harmonic rumble at higher RPMs. I have done the following: Replaced all fuel filters including the tank filters, diesel purge, adjusted valves, checked timing and timing chain, removed exhaust, removed and cleaned exhaust and intake manifolds, checked turbo, replaced all motor mounts, replaced injectors, did compression check (300 +-on test and balanced), pumped 100 PSI into combustion chamber with no leaks on intake or exhaust, replaced rack damper bolt, removed harmonic balancer, removed transmission amd flywheel, replaced torque convertor, cleaned banjo bolt and line, replaced primer pump, no vacuum leaks. I just don't know what else to do. I'm getting ready to replace the injection pump. Everything seems to be good with the head, but I'm leaning more in that direction. It sounds like a miss or a plugged exhaust. Kind of a chug-chug sound beginning at about 900 RPM. It's there at idle also, just not as noticeable, whole car rocks at idle.

Does anyone have any suggestions, perhaps someone else has had this problem and figured it out.

HELP!!!!
Bob

 

Have you checked air filter housing engine mount? The rubber bushings can strip from the bracket. Sometimes the bracket itself will fail at one point due to metal fatigue (vibration).
The air filter housing just bounces around on whats left. Just replaced my second one.
85 300tdt