My truck is a 2002 Chevy Silverado LS 1500 4x4, and around 60,000 miles or so I started to hear a knocking/slapping sound coming from the engine during idle. I know about Chevy piston slap because my 2001 Silverado had the bad knocking sound when I started my truck. This time it sounds different, not so much as a loud knock or slap, more like the lifter is not working properly. Has anyone ran into this problem on their truck? If so did you get any results from the GM dealership or from your own repairs?