What's the tach showing at idle?

Is it idling slower, when it's hot (and running rough)?

I've been thinking about my first reply to you, and I'm reconsidering it.

Reason: As I understand it, the purpose of the updated rack damper bolt (the gold one) is to correct for natural wear in the pump as the car ages. It's just a touch longer, which restricts the movement of the pump 'rack' when the engine is at operating temps.

The theory is that you always have to adjust idle to find a 'sweet spot' based on adjustment of both the idle screw and the rack damper (and some would include the ALDA as well; IMHO that's overkill).

Each engine is different as it ages. Some are happy to idle way down at 500-600 rpms, some want to be at 700 or more.

Perhaps you may want to consider getting the updated bolt, and messing with your adjustment. It's not something I recommend lightly, as it can drive you nucking futz, getting the sweet spot nailed down. BTDT on three cars, two weren't bad but the third nearly drove me insane. (And as soon as I got it just right, some ditz on a mobile wrote it off at an intersection.)

But before you go that route, you do need to ensure everything else is up to scratch -- no air leaks, dirty filters, etc.

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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