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Q: why do my spark plugs keep arcing from base to side of head.
on 1998 Mazda Protege

happens gradually at about 5weeks and continually gets worse until i have to replace them. I have replaced all plug wires. The electrode end of spark plugs look good. It arcs from the base where the porcelain insulator goes into the metal. They dont all arc at the same time . It is erratic and the car idles fine with an occasion mis. The hotter the engine gets the worse it gets especially under load. I had it put on computor and it says that i have bad spark plugs but it doesnt say why they keep going bad.
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You will typically see carbon tracking on the porcelain that leads up to where your plug wire connects if the plug is fouling (possibly incorrect anode to cathode gap) or if the plug wire or ignition coil is going bad. Since you have replaced your plugs and presumably use the recommended plugs and set the gap to the .043" recommended setting, it is probably either a wire or the ignition coil(s). If the problem suddenly appears and then goes away, it is most likely one or both of the coil packs that sit on top of the 2nd and 3rd cylinders. If it is continuous as it gets worse, it is more likely a faulty plug wire(s).
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