82 240D Shut off problem
 

Another topic reminded me of this quirk:

My mercedes usually doesn't shut off when I have my doors closed. If I turn off the ignition, the engine will continue to run until I open the drivers door, and then it will slowly come to a stall.

If I open my door and count to five, the engine stops immediately when I shut off the ignition.

It doesn't bother me so much, rather I think it's an interesting quirk, but I can't help but be curious as to why it behaves like so.

Any ideas?

Vacuum
 

leak in door supply line.

Mine did that in the early days of an IP shutoff valve failure.
Get out the mityvac, look for leaks, and check your lines for oil...