Rough Idle on 300TD

[callenderevent]

Now that the weather is cooling down in Minnesota, my 87 300TD is running rough when I first start it up and particularly when idling in neutral. Perhaps a little extra diesel smoke, as well. I always use premium diesel of at least 45 cetane. The car just has 66,000 miles on it and I think the injectors are original.

Also, I had the car to an MB dealer in July because it was dieseling. I thought the shut-off valve needed replacing. They said the vacuum lines needed cleaning out and it did take care of the problem. But now, 2 months later it is doing it again, although not as bad. Before, I usually had to push the stop button to turn it off when it was warm. Now, it just runs on for a few seconds.

Does it sound like I have two unrelated problems, or one that is manifesting in more ways now?

Thanks in advance for any input.

John


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[123 300D driver]

Have you ever cleaned the injectors with (a) and Italian tune-up or (b) with the Lubromoly or Redline injector cleaner?

[callenderevent]

I have never used an additive in my 87. My MB dealer recommends never using additives in a diesel with a trap oxidizer. Over the years, I have used injector cleaners and fuel supplements in my 83 300TD, but it doesn't have a trap oxidizer.