Just went over some previous posts - is there supposed to be a gasket between the cap and the rotor?

There is still the coil that could be the culprit.....is that difficult to change?

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K