[s-cars] missing electrode (bucking under full throttle)

[Michael Mulholland]

well you're not alone in the missing electrode dept. i have 4 of them on my desk. one was newly installed by the dealer and lasted only 500km. i think that its bad plugs. the plug works loose and overheats and somehow the porcelain shrings from the plug body and can be rotated and wiggled. this allows combustion gases to escape thru the plug and causes the oily residue. when the electrode disintegrates from overheating the gap becomes wider and wider requiring and ever higher voltage to bridge the gap. at some point, if the the coil doesnt breakdown first, the spark will actually jump through the lead to the head. i have replaced these bad plugs temporarily with champions for a test and the champion never failed in 2 thousand km and didnt come loose or show signs of lean mixture or overheating. i have since installed a new set of the correct plugs and so far so good with about 5000 km travelled. car is bone stock with no mods.
mike

95 s6
87 5kcstq
93 90 csq
54 austin conv.