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Old 02-07-2014, 08:33 AM
Mölyapina's Avatar
Mölyapina Mölyapina is offline
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Join Date: Oct 2012
Location: Chelmsford, Massachusetts
Posts: 4,353
The rough idle may be an altogether separate issue. Is the idle jumping around, or is it mainly shaky? If it's mainly a rattling-your-teeth-out (or rattling-your-dentures-out if you've ignored it for long enough) issue, the most common culprits are:

Motor mounts
Engine shocks
Nailing injectors
Rack Damper Bolt
Maladjusted valves
Filthy engine

For motor mounts, Roy (whunter) has specified a way to test for them that I can't remember right now. The engine shocks I would leave for now. Rack damper bolt adjustment instructions are here:

1985 300D Rack Damper Adjustment.

Valve adjustment instructions are all over the net, and the filthy engine could be corrected via a diesel purge -- DieselGiant has a great set of instructions, but know that NAPA carries that purge fluid for MUCH less than DieselGiant.

EDIT: Ha, I forgot nailing. Nailing injectors have a distinct clicking sound that can be heard over the general engine rattle -- kind of like the gnome who lives under your valve cover and makes the engine work right is building himself a house . If your injectors are nailing, I recommend greazzer for the rebuild unless you want to do it yourself, at which point you'd need to find a pop-tester somewhere.
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."
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