Whats wrong with your distributor? i can see that there is melted plastic on the diaphragm i am guessing that maybe there is a way the electricity is finding away to escape to some other wires or metal surfaces? i had the same problem with my 4runner where the spark plug wires were melted from the heat of the exhaust manifolds exposing the wires and the current was directed somewhere else instead of going to the spark plug making it run on 5 cylinders instead of 6