Mechanic willing to help

Please for the love of God, make sure that the overhead was run!!! And please let it be done by a mechanic certified in the MX-13! I can't tell you how finicky the MX's are about their valve adjustments!

 

Were the new injectors calibrated to the ECM via Davie4?

If so, then I'm starting to think unit pump. Testing these are easy. On the EPA13 MX-13's there are two unit pumps that provide the high-pressure fuel to the common rail. These are located where the unit pumps would be for the #5 and #6 cylinders on EPA10 and earlier MX's.

-With key off, unplug one of the unit pumps.
-Go on a short test drive (bobtailing) with it unplugged. Please do this in a rural area with light to no traffic.
-If the engine feels to be running and performing the same, the unit pump that is still plugged in is good. Proceed below. If it can barely get up to speed, the vibrations worsen, or the truck has a severe miss, then you need to replace the unit pump that is still plugged in.
-Stop the truck and turn the key off. Wait 90 seconds after key-off (one key cycle in Paccar terms).
-Plug in the unit pump that was unplugged and key-on, engine off for 90 seconds.
-Key off again for another 90 seconds.
-Unplug the other unit pump.
-Start the truck and take it for another short test drive.
-If the engine feels to be running and performing the same, the unit pump that is still plugged in is good. If it can barely get up to speed, the vibrations worsen, or the truck has a severe miss, then you need to replace the unit pump that is still plugged in.

 

No problem, report back with what you find.

 

Yes, but it would eliminate the clutch disks if it still does it with the clutch brake engaged. However that would still leave the pressure plate and flywheel. Chock the wheels, take off the inspection plate, and run the truck. Look up there with a fairly bright flashlight and try to see if you can see anything. Safety glasses are highly recommended for this...