Ahhhh, okay if it's intermittent then have you found a commonality to when it occurs?

If, for example, it's after extended highway use (and returns to a smooth idle after a while once you are off the highway), that isn't that unusual. It's probably wear in the pump governor. My first SD did that all eight years I owned it.

If the behaviour is related to ambient temps, or engine temps the longer you drive, then it could be an idle speed adjustment/rack damper bolt (adjustment or wear) issue. Rack damper bolt wear means you need to upgrade to the gold bolt.

Just to further complicate things: I forgot in my original list to include air leaks in fuel system. But that would produce fairly constant symptoms, albeit likely worse with the motor fully warmed up.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22