My 1988 300E has had the intermittant stalling problem for years as well, and recently has started running rather roughly at lower idles. My car will stall coming to a stop or turns, but it will also stall at highway speeds. Sometimes I can put it in neutral and turn of ignition and fire it right back up, but other times I have to pull over, park, and let it sit for anywhere from a few seconds to a few minutes before it will restart. Usually it won't stall again for weeks to months. Sometimes, it will go through a period where it will stall a few times rather quickly, like minutes apart, but this is unusual.

The rough idling part is rather new.

When I am sitting at a stop the vacuum gauge is about halfway and fluctuating. If I turned on the AC it will really go back and forth, hunting up and down.

I definitely will check out the air flow thing, but any other ideas?

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1999 Mercedes ML320
2002 Mercedes 230K