Have silverado with the 5.3 vortec, owned since last october and no issues until roughly 2 months ago when service engine light came on. Had codes pulled on it and its P0300. Replaced all spark plugs and EGR valve. Everywhere I go people and mechanics tell me different things to do and check. I also read on older threads that there was confusion on what the spark plugs are supposed to be gapped at. Looked on my truck and the sticker is worn off so i cant read what its supposed to be. Autozone says .040 and other resources say .060 So not sure on that one. I have no idea where else to start looking or the cheapest/simplest things to check. Any advice/help would be fantastic! Oh I also looked all over the engine and at every vacuum line I could see to look for any cracks or damaged hose lines and cannot find any.

 

Did you figure out the problem. I’m know the gap is supposed to be.060