Hello bluebenz,

I did it on my 260 E, 1988, 400 000km, I agree there is a need for cleaning it.

Long milage and riding in cities at very low speed makes vapor oil to condense in the body and prevent idle opening to remain correct.

I just had to remove the assembly distributor+ air flow sensor (all together, no need to dissamble them) and cleaned it with good cleaner (I changed the gasket and the 2 small connectors for the vaccum lines).

Take the opportunity to clean also the three small holes for the vaccum lines.

Do not change the setting of the flap stop screw (what I did unfortunately and never found the method to adjust it except by trial and error). I opened a thread on the matter and posted pictures.

Would you do it, could you please post pictures of the inner side to show the position of the flap versus the two holes when closed ie at idle.

Good luck.

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Keep us posted especially if your problem is solved
Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class, 220CDI, 2009, W204

Sold: E-class 260E, 1988, W124, Wonderfull car sold after 489 000 kilometres of reliable services (engine M103, clutch, brake system and 5 speed manual gear box all original).

Sold: E-class, 320CDI, W210, 2000, 225 000km