My 84 300td with 270,000 mi. runs rough both at idle, and same at higher rpms...so this is not just a rough idle question. At idle, and at high rpms, the engine has a vub, vub, vub, vub sound instead of a nice even clakety clakety......this is especially pronounced at between 10 and 15 k rpms. My previous experience with rough idle only, is that at higher rpms, the engine usually smoothes out beautifully. But now even at highway speed, I can still hear and feel that vub, vub...

I recently:

- installed new timing chain
- new fuel filters
- adjusted valve clearances
- measured cold compression...300, 275,260,280, 250 (I now realize I should have done this on hot engine!)
- removed all injectors, and replaced with another set from previous car...no difference (I should have spray patterns and pop pressure tested)
- checked inj.pump timing...drip tube method....exactly 24 deg. BTDC
- checked all fuel del. valves on inject. pump...all clean and free moving
- cracked open hard fuel lines on each injector while running....all had noticable bad impact on running engine.

I have not tested cam shaft timing (earlier post today), and I should check compression while hot. Any other thoughts?

I am suspecting valve on #5 cylinder, but I havent done a leak down test.

Thanks,

Mark

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1984 300TD Wagon, 407,800 mi (current daily driver)
1985 300DT Sedan, 330,000 mi (gone to that great autobahn in the sky)

I don't know, but the compression difference doesn't seem like enough to point to a bad valve making it run that rough.

I'm perplexed with the vub vub. Is it a fast paced knocking vub vub? Or more like a whine vub vub. How is oil consumption? How is fuel consumption? Any big changes in those categories? Before I did a new head, my #5 had 100lbs. on a hot engine! And I actually had a pretty good idle when she warmed up, and definitely smooth running at higher rpm. So I wouldn't fret over the lower number you have there. You didn't mention air filter, but I doubt that would be a problem here. Describe the noise a little more and let us know about fuel and oil consumption. But so far, I'm stumped.

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1998 E300D, 287k, barely broken in.

Have you tried switching the injectors around?

Tom W

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Have you checked your fuel filters? I had a similar problem and my fuel filters had reached the end of their useful life! Cleared the problem right up when i put new ones in!