[silvereagle07]

I had this same noise in my buddies tahoe. The noise was just as you described. He was about to replace the engine because it sounded like a lower end knock. But before I ordered the engine I looked in the cylinders with a scope and saw a serious build up of carbon on the pistons. One spot had come loose and sounded like above noise when it was up to driving temperature. I ran two systems of BG fuel system cleaner through it and drove it hard until the carbon came loose and blew out of the exhaust. The product is not something you buy at a store. It's ran through an air pressurized system into the fuel system. It works believe me. He is still driving it daily. Its been almost two years.