I used an analog (needle) dc voltmeter this time. When I grounded #4 it went to zero. 2 seconds later, the needle dipped to zero then back up quickly ONCE. I ground again and it again does ONE jump.

Could it be that I don't have any codes?

So what could be causing this loss of power and nailing at idle? Time to clean the injectors?

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1994 E420 43k (pickup, solid)
1990 300D 2.5 127k (sold) (now driven by friend)
1991 300D 2.5 73k (sold) (incredible car)