my 81 240D has been running fine up til this morning... when it started running a bit rough and now there is a little bit of clanking going on in the engine area.. its no too bad- i've read on the forum people talking about 'nailing' where it sounds like metal hammer hitting metal., its not that bad, just sort of a diesely clanking sound- i have a 77 240D that hasnt got much love from me yet, and it clanks a bit when it goes, so now my 81 sounds a bit like that. i also have a ford psd 7.3, same thing, has that school bus diesel clank thing happening..
BUT, unlike my PSD or the 77, the 81 is running rough with the clanking, so it seems to be more of an issue. its kind of an uneven chugging during idle rather than a smooth purr. almost like it might die, but it doesnt. it still gets up to speed on the highway, just feels a little rougher and a louder chugging & clanking noise when running.
i realize this is probably very vague,, and could be lots of things, but any suggestions on where to start? i for 1 want to make sure continuing to drive it isnt going to be harmful, and 2 how to get her back to a smooth purr.
i havnt done anything to it recently that would have changed things, or affected how it runs. i recently changed fuel filers, and topped off the engine oil. i havnt done a valve adjustment before, but have been meaning to learn how to do one, im not sure when the last time the PO had one done.

from what ive read around here, people seem to suggest injectors, IP, vacuum pump... ???

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1981 240D ... 265k
1977 240D ... 265k
1977 240D ... 250k