Hello Forum! Lately,my high high mileage '82 300 sd (355,000) has been intermittently running rough with the shakes. Motor mounts were just replaced and valves are adjusted properly. The scenario is from time to time, I will pull in to my driveway and the engine will start to shake strongly and act as if it is missing and behaves like it has a bad motor mount with lots of shaking. It does not do this everytime which makes me wonder what could cause intermittent rough engine running on a diesel. Could a failing lift pump cause this or other? Injectors are new and were properly calibrated by Bosch shop. Perhaps a clogged main fuel filter? Any thoughts out there? Thanks!

My 81 300SD does the same thing. Sometimes I will be idling at a stoplight and almost rocking back and forth and magically it will settle down to a smooth idle - almost like a computer took over the engine management (but it's an '81). I have tried to remember whether it idles better in cold weather or warm weather but have not figured it out.

It absolutely seems like something starts working and the rough idle just goes away. 257k miles and I am the first owner.

Could not hurt to change th Spin-on filter.

A small Air leak could form a bubble in the Fuel Injection Pump Housing; and when it gets big enough all or part of the bubble it could pass through your Fuel System into the Injectors.

It could also be your Fuel Injection Pump Pressure Relief/Bypass Valve is having issues. It is a Ball Bearing with a spring on it. Perhaps it does not seat well all the time.
A very long thread on the above.

Could be one of the 2 Valves in the Lift/Fuel Supply Pump are not seating well.

Somewhere in our DIY Repair section they have tests for both of the above.

Then there is the Fuel Tank. Restricted Screen (stuff could be floating around in the tank a cause issues only ounce in a while) or a restricted Tank Vent.

In this last year I have been reading of people haveing enough Crankcase Pressure due to the Blow-by that it had an effect on the Vacuum Shut off; pushing it partly in the shutoff position. At least 2 had restrected Blow-by plumbing.
I know when I blocked my Blow-by Tube with my thumb in about 7 seconds my Engine was trying to shut itself off.

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84 300D, 82 Volvo 244Gl Diesel

I recently experienced just that issue. I think that I had an intermittently sticking delivery valve on the fuel pump. I installed a pump overhaul kit and my idle smoothed out tremendously. Acceleration was also significantly improved and the transmission now shifts a bit better. '82 300D.

Does this happen only with a hot (operating temperature)?

If so, an adjustment or replacement of the rack damper bolt/pin may be in order.

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83 SD

84 CD

pop the hood and look for any fuel leaking on the injectors or the pump. a customer's car had a rotten miss. an injector line was loose.
air in the fuel system could do the same thing by blocking an injector from firing.

Thanks will check all of the above -it seems like an injector missing so today I thought I would loosen injector lines one at a time to see what happens. It also seems fine at speed but coming home or idling up to a start I get this crazy shaking -again, just replaced all mounts -

are you talking about the drain tube back to sump being partially blocked? How to test? My shut off at engine shut off lever has been sketchy lately . . .

Car starts up fine and idles perfect when cold but after several minutes of running and reaching operating temperature, it starts shaking again at idle and idling up to a stop -rack damper is fine also. My emergency shut off appears to be non operable . . . related? Anyone?

If the linkage from the shut-off lever to the IP is out of adjustment, then the stop lever will not shut the engine off. I did this after following some low power posts, regarding taking up slop in the throttle linkages and making sure WOT caused the IP to go to max. I do not think this adjustment issue will cause the other issue you are dealing with, though. Someone else chime in on that please.

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Thanks,
Mark in NC

"Spark plugs?...We don't need no stinking spark plugs!"
1985 300SD "Der Silberne Schlitten" 420,000 mi


Wish these were diesel:
2003 Ford Club Wagon 130,000 mi

Hmmm .. ended up doing the same and then the manual shutoff stopped working but i didn't notice for awhile because the key shutoff still worked.

Didn't cross my mind that tightening up the the throttle linkages could have messed up the manual shutoff. Ended up with a huge increase in power and throttle response, the engine is also normal otherwise.

When I press the manual shutoff, there are results in that the engine starts shaking/missing.. but not enough for a shutdown.

EDIT- Actually, it was all awhile ago and just remember that I tried the manual shutoff awhile after the adjustments because the key shutoff started acting up/not working but then that problem (key shutoff) went away.

Given all that, I would think that if the linkage(s) get loose/out of adjustment, that could cause problems and would be easy enuff to check.

EDIT II - forgot that when the key shutoff acted up, changed out all the old, hard cracked rubber vac connectors and then the key shutoff worked again.