O2 sensor should not cause it to stall while driving, it will simply default to a fuel wasting rich setting if it gets an illogical O2 reading....

I'd bet on the crank position sensor....that's what it was when my 300E had those symptoms, only did it once warmed up (resistance changed from temp). On mine I have the california LED light code plug, so it actually gave me a CPS illogical code after it stalled a couple times.

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