what would cause damage to#4 spark plug at tip? on 2002 Mazda Tribute

Dealer found #4spark plug damaged at tip. They had replaced #4 coil a year ago. . Ran better but not great. Last week started stalling and barely could get to 30mph. Engine light came on. Found codes P0354, 0301, 0303 0305. Said something in combustion chamber caused damage. Recommends tear down to inspect heads. Will cost in the range of $3000 to fix. Could the damage on #4spark plug have something to do with the coil replacement the year before.

by in Anchorage, AK on April 23, 2012
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1 answer
ANSWER by , April 24, 2012
Could be that it could have had a detonation problem due to restricted exhaust. Have see catalytic converters stop up and cause this type of problem. The engine has less power due to not able to get all exhaust gases flowing though converter. nAlso the P0354 indicates it may have a shorted coil or bad PCM.