Did you ever resolve this problem?

My recently purchased 300E runs excellent with one exception. It sometimes stalls right after starting or stumbles for few seconds until idle stabilizes.

I checked the duty cycle from X11 connector and here are the results:

Ignition On, Engine Off: 50%
Engine at Idle: 48%-54%
Engine at 2,500RPM: 68%-72%

What would cause it to be 50% and not 70% with engine not running?

Have you replaced your OVP?

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

I have not and actually, ABS light came on few times while I was testing the duty cycle.

Sounds like the classic OVP failure symptoms.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't