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Rough idle after warm up 1985 300D

Submitted by c47captain on 1 September 2010 - 3:05pm.

I bought this car Nov 2004 and it had a rough idle when warmed up. In an effort to solve this I set the valves, replaced the injectors with rebuilt ones. No help. Meanwhile, and for other reasons, I installed a rebuilt engine Jul 2006. By Sep 2006 it too was idling rough after warm up.
Once again I verified valve settings and replaced the injectors with rebuilt units. I also replaced and adjusted the damper bolt, replaced the the motor mounts, transmission mounts and the engine shocks. No help.
In Jun 2007 I went all out and put in a dealer supplied rebuilt injection pump. No help.
So here it is Sep 2010 and the rough idle persists. It might be good to mention that I did retain the turbo charger and the steel injection pipes from the original motor and put them on the rebuilt engine at the time of installation. I also note that the turbo does have an internal oil leak and I plan to overhaul it soon. I hope some one reading this has been down the same road and found a fix or some steps they found to work. Thanks for all your help. Joe

‹ Diesel Fuel Lubricity 1980 300D engine temperature ›

Rough Idle?

1 September 2010 - 3:30pm
Kent Bergsma

This is what I call a mystery. To help diagnose try to explain what you mean by rough idle. Is the engine misfiring (real rough idle)? Does the engine shake or does it loop (surge)? Or does the engine just have a high level of vibration (felt in and through the car).

Have you tried running it directly on diesel purge to see if any difference after it warms up?

And curious - were you a C47 pilot. My dad was an instructor in C46 and C47 in Texas during the war...

Thanks for the response. It

1 September 2010 - 4:07pm
c47captain

Thanks for the response. It is rough, shakes in about say a 4 inch arc when viewed at the valve cover and shakes the star in about a 1 inch arc i suppose. I just put purge in the tank. I see what you mean about doing a direct feed with the purge and I plan to do that next if this thing is still shaking after the tankful goes through. I could easily imagine that the internal oil leak in the turbo may have carboned up the motor much more much quickly than just normal fuel combustion would have. As for the c47, your father was fortunate indeed. My c47 time was in a corporate DC-3, in 1999/2000. Nothing else even comes close! OK, back to the car trouble: I have heard of steel injection lines internally corroding and causing fuel cavitation. I will post whatever I find that clears this problem. Thanks again, Joe