82 300sd shakes help

Hay all, Thanks for the help that several of you have given to me on the many questions I have asked getting my 82 300sd engine changed out. It took two engines, the first was a real dud! This one seems good I
think. It starts without hesitation and runs good with a lot of pep.
The problem I have now is that at an idle the engine surges or shakes. I don't think it is motor mounts it is too violent to be caused by soft mounts. It is noteworthy that the fuel in the tank is 7 months old and that I have driven this motor for about 30 miles on the road. The feel on the road is normal. At 700 RPM the motor shakes. When you start the engine it comes right up to 700 RPM and runs real smooth for about 30 seconds and then it starts to shake. It dose not matter weather or not the engine is cold or warm, it is smooth after starting and then starts to shake. If you kill the engine it will repeat this. I have turned the rack damper in turn on the injector pump with no improvement noticed. I, not knowing much about this adjustment did not try any further adjustment. Any one out there got any Ideas? If I can fix this I think I got a good engine.
Thanks all, Bruce Buchanan Brujan@(NOSPAM)the-i.net najurb
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Your engine seems to be OK but has some problem that allows it to oscillate, some ideas:
The engine should idle at 750 rpm, the idle stop set screw is between the injection pump and the block. A deep socket and large flat blade screw driver is needed to adjust it. I suggest a one turn (clockwise) adjustment to raise your engine's idle to say, 750 to 800 rpm. It's not an exact science. Write down the adjustment so you can reverse it if necessary.
The rack damper pin or screw is spring loaded and stabilizes the fuel rack. Otherwise, the rack picks up the engine's oscillations and that causes the engine's speed to oscillate - which makes the shaking worse. There's a "new" version of this pin which has a stiffer spring, about $25.
The rack damper adjustment has two limits: Too tight will cause the engine to stall, too loose will allow the idle to wander so low to stall the engine when hot. That happened to me.
These engines also have a small shock absorber on their left and right motor mount, does yours?
The left and right motor mount pads are NOT interchangeable, one is designed to be compressed, the other pulled by the engine's torque. I hope yours are correct.
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When my 83 300SD had the shakes at idle after a run a can of diesel purge direct into the engine cured it. hank wd5jfr

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