my 380 sl was breaking up. The rotor was burned out. I mean the brass end was gone and the center of the arm was gone half way up. I don't know how it ran at all. the cap & rotor only had about 3000 miles on it, having installed it after buying the car with 107000 miles on it.
The cap looked good except for a slight discoloration on one contact. I found out that ignition wire was bad so in went a new set.WOW! BIG$$$$$ That was 1000 miles ago. Going on a trip with it Friday, so I checked the rotor. The brass end is OK but the brown end of the rotor has turned black and is slightly pitted. the cap looks like a good 40000 mile cap would look like. Any one know what could be causing this?

Just a shot in the dark here. I had the same problem with a chev. 350. Stubburn as I am about taking it to a shop, I wore out the center deal on 3 rotors before someone mentioned that "...there was a resistance in the flow of current to the plugs". I replaced the ignition wires (I think it might have been just the coil wire (?) but I replaced them all, as they were old) THAT SOLVED THE PROBLEM!!!! Good Luck Matt

I'm inclined to agree with the " too much resistance " theory.
Might want to get a scope test done, to pinpoint the problem.

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2007 C 230 Sport.