A friend of mine has a 1986 Ford Explorer. It's runs very rough from 700
(idle) to about 1500 RPM. He's found several things wrong and fixed them,
but the problem is still present. He took it to a mechanic who removed the
plugs and found the element (for lack of a better word - where you gap the
plugs), burned totally away - it was not there any more. The mechanic
explained this as a pre-ignition problem, it's getting way to hot - and he
was not surprised the pistons did not have holes in them. The compression
is
good, but the mechanic seems to think the valves are being pushed into the
valve seats very hard. To me it seems like the valves are closed to long
when the engine fires - but I don't know.
Can someone explain pre-ignition in more detail than it fires early. What
is
the cause of pre-ignition? A timing belt problem? Seems the timing is
off,but checks OK.
Thanks
Scott
