I'm guessing something is happening when the o2 sendor begins to send signal. Like the system is in lambda limbo

I was thinking maybe a coolant temperature sensor was giving off a weak signal?

We use different systems, but the underlying idea between the two must be similar?

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E