I have a 1991 300D which runs pretty well, except for a somewhat rough idle. I have replaced the DV seals already, and checked the fuel system for leaks. The motor mounts have also been replaced. Diesel purge done. Next on my list are the injector nozzles, but I want to confirm first if they are the source of my rough idle.

Diesel Kleen or other fuel additives seem to reduce the vibration at idle, which is not a surprise. What IS surprising is that the idle smooths out dramatically in hot weather (above 80 degrees F). What could be causing this?

Is the idle improvement due to lower viscosity of the fuel? If so, would that indicate worn injector nozzles?

I have searched the forum and didn't find anyone with the same observation. Any help from the best & brightest would be appreciated!

If your injectors are original or have many thousands of miles on them you're not going to regret having them rebuilt. I hope that solves your rough idle situation. It just may. Either way it will be an improvement.

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

Did it run smooth while running on Diesel Purge? Mine did.


Chris Dragotta
Owner
No Pressure Cleans
Benson, NC

It was a little smoother, but not as smooth as when the weather is hot. It definitely needed to be done though - the return fuel turned jet black. I have been putting a bit of Diesel Kleen in every tank to help take care of the rest of the gunk.

Phillytwotank - Injector nozzles are definitely on my list. I like the looks of the Monark kit from the vendor that rhymes with "her lady's force"

Holler at PP forum Member Greazzer. He's the resident injector service man. Quality work. Great Price. IMO a lot easier to just sent them off to him rather than trying to acquire the tools and knowledge to DIY.

__________________
Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

Thats pretty normal for all of these IDI diesels but the liquid filled engine mounts are good at muffling out that vibration. If the difference is very noticeable its time to change engine mounts.

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CENSORED due to not family friendly words

Getting injectors cleaned, nozzles rebuilt and balanced will reduce noise significantly and increase smoothness.

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Strelnik
Invest in America: Buy a Congressman!

1950 170SD
1951 Citroen 11BN
1953 Citroen 11BNF limo
1953 220a project
1959 180D
1960 190D
1960 Borgward Isabella TS 2dr
1983 240D daily driver
1983 380SL
1990 350SDL daily driver alt
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