HELLO everyone its my first time on this site and just wanting to get my feet wet in hear and see if i can get a lil help about my problem. i will try to get a video of it, but when i start it up it sounds like a slight lifter to a slight knocking sound then it goes away but i think i still hear it if i take off pretty hard. I baby the truck and it seems to run fine just that noise scares me a lil, so I dont really get on it like i would sometimes. Truck is nothing crazy, 00 yukon slt 5.3 4x4 with 141k on it. Also any ideas of what this can be, and I dont think the truck ever had a tune up, so all tips on the noise will be greatfull, and tips on it to run better will work too

 

These engines are notorious for lifter tap on cold start up. Also check for any exhaust leaks around the manifolds.

 

Could be piston slap, also known as cold start knock, it's very common among the GENIII engines. The piston has a short skirt and will rock slightly in the cylinder until it is warmed up and expands. GM calls this "characteristic" and claims that it won't hurt anything. My 5.3 does it for a few seconds when it's really cold out. It could be something else such as a lifter, but the piston slap is the monst common.

 

Lifter tap or piston slap, do to the short skirt on the pistons. Like stated they are notorious for this. Don't worry. It is more abundant in some then others...

 

sweet thanks fellas. Im a newbie here on this site but im glad i was introduced to the site, thanks fellow truck fans.
All other advice will work too