Stumbles only when warmed up
 

96 3500 HD chassis cab. I have had it about 2 years and the person who sold to me was dishonest with regards to the maintenance and mileage (odometer works when it wants to) so I don't know the history or whats been done.

Couple weeks ago it would hiccup on the highway when either towing or just driving. Progressively got worse to the point where it would stall if you weren't flooring it. It always starts back up.

I have a new relocated PMD and have replaced two of them and it doesn't act like a dead PMD. I replaced the OPS, no change. I replaced the lift pump, no change. Did a million tests to make sure there wasn't some problem with the fuel tank pick-up, no change. Replaced several grounds on the passenger side and put new terminal on the battery, no change.

When I start it up and it's cold it runs ok (it does sound loud like a cummins diesel now), when it gets warm it starts to stumble, stutter, rev on it's own and stall.

Pulled the codes and got this:
P0251 -- Injection Pump Cam System
P0335 -- Crankshaft Position (CKP) Sensor Circuit
P0370 -- Timing Reference High Resolution
P1218 -- Injection Pump Calibration Circuit

To me it seems like maybe the IP is bad, but it also seems like maybe something else is out of whack and when it gets warm the computer changes the timing in a bad way. Looking for some more experienced input, use this for a work truck and renting a replacement is really eating up what little money is out there to make :argh:

P0335 -- Crankshaft Position (CKP) Sensor Circuit

I would start right there with it, check out that sensor first.