I am trying to 'fine tune' my idle speed on my '78 300D - does anyone know how to measure rpm's on this car? The FSM shows a "revolution counter", which I don't have, and even if I did, I don't know where to connect it???

Any way to hook up a tach?

Thanks,
Ryan

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RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE