1984 300td runs rough....will not idle<<HELP!

[danton84]

I recently purchased a 1984 300td w/ the hopes of saving this car from its
otherwise doomed life. The previous owner had been experimenting w/ WVO and Bio Diesel in a single tank system. He stated that while on a trip he parked the car to eat and when he came back out he could not get the car to start....he finally got it started however it would not idle.

I drove the car 100 miles home...it runs great at highway speeds, but as your RPMs drop to around 1000 it starts running very rough....if you let off the accelerator the engine will die. I did notice on the drive that after letting off the accelerator it would take awhile for rpms to drop off like something was hanging up....checked linkages and all good.

The problem its not in the tank. I have changed fuel filters, and swapped out the injectors and lift pump, but the car still will not idle.

I still need to adjust the valves, but if that doesn't help I am out of ideas. I am afraid that the problem may be in the injection pump...I am needing some guidance so I can get this car on the road and give her the life she deserves.