My Mercedes dealer was unable to diagnose a problem with my well-maintained 2001 E320 wagon I have during the winter. It has 150,000 miles.

When the temperature is below freezing, the car starts fine, but stalls once I put it into drive, even if I let it warm up beforehand for five minutes. It takes another five minutes or so before the car will keep running once I put it in gear.

I once let it run a full 15 minutes before I put it gear. It tried to stall even then, but didn't. Once the vehicle drives off, there's no problem until the next morning.

The dealership says it is NOT the cold start valve. No error codes appear, either. They raised the scary prospect that it could be transmission related, but it was just a guess.

Any insights?