2002 Chevy Silverado

The noise is most likley carbon buildup on the pistons. You can fix this with some goog carbon cleaner like GM Top Engine Cleaner.
You will need to remove the spark plugs, disable the ignition coils, pour 1/4 bottle of cleaner into each cylinder (takes 2 bottles), allow it to sit overnight, crank the engine over a couple of times, install the spark plugs, hook up the coils, rinse the engine area with water, start the vehicle. (Don't get the cleaner on painted surfaces)