Was the knock sensor checked or replaced? What you described is usually caused by timing that is too advanced. The knock sensor has a role in where the timing is to be set. It tells the computer the exact point when a ping will begin. At that point, the computer is to retard the timing or keep it at that point. If it is bad, it can cause your problem.
Let me know if that was checked.
Joe
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Thursday, January 7th, 2010 AT 8:48 PM