I've experienced this problem twice in my short Pilot life.
The first PoofKaboom was due to not knowing that the Pilot I had just purchased was set up for high octane race fuel. By using regular 93 octane fuel, it caused a premature meltdown of my piston and cylinder head (or so I was told). The end result was extensive pitting of the top of the piston, the cylinder head dome and nasty scratching of the cylinder itself.
The second time was Thursday of last week when I unexpectedly drove into Lake Okeechobee during a wide-open throttle run at night (long story). Either way, I could not maintain idle after coming out of the thigh-high water and knew immediately something was wrong. After performing a compression check after cool down and coming up with only 75lbs of compression, I confirmed my fears. Tonight, I tore her down only to find the same thing I had found when I had the unknown race fuel setup. The top of the piston and the cylinder head dome was pitted like swiss cheese. Fortunately, the cylinder itself suffered no scratching at all because I had it coated with the carbide process at Bore-Tech (in my opinion, this process is a VERY necessary must have!).
My dilemma is, I don't have any trashed bearings and my intake is filtered twice. What actually gets in between the piston and the cylinder head to cause the swiss cheese effect? Is it part of the actual piston that breaks off and causes this? Please enlighten me! :?