Rattle

Have a 1999 Silverado with 4.3 V6. 80K miles. I get this rattling, knocking, pinging? (dont know the difference) sound at nearly all RPM ranges, but mostly between 1200-2000. It sounds just like my old 454 Buick Wildcat did when you stomped on the gas(although quieter). I have read about the TSB, but don't know how to diagnose. Also of note: California car, went to Iowa and ran 89 w/ethanol, and now am in Arizona running not so cheap, but I'm sure, crappy 87 octane. Problem seems worse in warm weather. Its never louder than the radio.

So is this piston slap, valves, fuel problem,etc.?

It hasn't caused any actual problems, just concern, as I plan to keep this car for at least 22 years...then make my kids drive it to school. Otherwise, the truck is really a pleasure to own.

thanks,
Phil

Sounds like fuel related pinging... you might run a tank of 89 octane or put some octane booster in it to see if it cures the problem

Try changing the fuel filter as well.