could be oil from valve cover gasket or not changing plugs wires
It usually means too much fuel or not enough spark.
Leaking valve guides in the head will cause oil to get around the spark plugs.
It may be that the spark plug is dirty. Try cleaning it
heat causes pressure, pressure causes friction, friction causes spark, spark causes KABOOM! all in a split second
It is black.
friction
No spark.
ummmm you fried it
No spark from coil, bad plug wires, or bad plugs.
Time to replace seals, this usually causes misfire.
if the spark plugs are black because your car is running too rich. your plugs are fouled.
If you touch the sparky thingy that could cause a spark through your body which would be a bad spark. Am I close?