If you have a turbodiesel, yes some pulse in the return line is normal. That is why the turbodiesels have the cigar-shaped hose on the return line from the filter canister.

Does yours have the correct hose? I have heard tell of cars having idle issues, without it. Most do not (including in my own experience).

Other common reasons for lopey idle:

- air leak into fuel system (loose clamp, leaking primer pump, etc.)
- idle speed set too low
- need to upgrade rack damper bolt (aka rack damper pin, aka rack pin).

The last is the most common. You should find lots of info if you search on it.

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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