This is for everyone who has a 2000-04 Chevy/GMC/Cadillac Truck engine. I have had a noise in my engine that started as a tick sound and progressed into a knock. At times I wondered if I was going to throw a rod or something - it was awful! Long story short, I have searched the Internet and asked mechanics until I was blue in the face with frustration. I finally tried something a mechanic in Greenville, Texas suggested and it worked. Apparently Chevrolet has acknowledged a problem with carbon build up on the tops of the pistons. I know, this sounds like some hocus pocus load of crap, but read on. I went to the local Chevy dealership and bought 4 cans of "Top Engine Cleaner" (Chevy part number #105002 @ $6.54 a bottle). I then went home and removed all sparks plugs, used a funnel with rubber flex tube on the end to funnel the cleaner into each combustion chamber. I guess I put about 1 cup of this cleaner into each chamber. Man this stuff stinks to high heaven (warning label says "known to cause cancer in the state of California... good thing I don't live in California - joke). I then let it sit over night to disolve the carbon build up. FIRST THING - change the oil! The cleaner will seep down into the crank case. After I changed the oil I turned the engine over to force out the cleaner from the pistons (I should have stuffed the manifolds with towels to prevent the cleaner from going everywhere). I then put the spark plugs back in and turned it over. It took about 1 to 2 minutes to get the engine to start. Guess what? The knock/ping is gone. I mean it is completely 100% gone! There is no trace what so ever of a tick or noise at all. This process might or might not work for you, but I swear on my life this story to be true. I highly suggest you try this if you are experiencing the same engine noise.
