OK...geez. It seems like I have a new issue with this car every day (probably self inflicted from trying to fix everythine myself). '91 300E again...car died on me today at work (drove there super good...great idle..everything). After battling with different ideas and almost draining the battery, I pulled the plugs. They were all black. I have noticed that around the base of the engine top cover there is recently something leaking but not sure if it's oil or coolant. Is this a rich gas mixture setting issue? If not, what might it be? I like working on this car but not every day Could the wrong plugs cause this? I went and bought 1.99 copper plugs...started right up and came all the way home (50 miles). When I check them tomorrow, what should I be looking for?