I have a 1998 protege 1.5 litre. Changed spark plug wires and spark plug. About every 5 weeks spark plugs will begin to arc randomly and progressively get worse over the next 3 weeks untill i have to replace them . Had it put on computor and was told plugs are bad. I keep having to replace them . It runs fine after i change them but then starts arcing in the spark plug well. I noticed it is arcing from base of ceramic insulator to the head. Never seen this before but can it get too much voltage or not able to disapate heat fast enough.
Spark plugs arcing from plug to head. on 1998 Mazda Protege
you might have a cracked plug or a bad wire
posss cracked plug insulator
I've seen computers detect 'misfire'(cyl. #) , but not specificaly a plug, that's impressive! ........Silly question , but are you using a torque wrench to put the plugs in (most are only 12-18Ft. Lbs.)? Also are you using OEM parts , Or Plugs and wires from Advance Auto Parts? Are the wires getting oil-soaked by any chance? Has a compression or cyl. leak-down test been performed at any point? Are plugs oil fouled when removed? Are all plugs wearing the same? Sounds like something major is being missed or ignored .