tennerv8

iTrader: (7)

Hey guys, I have a '99 gmc sierra with a 5.3 LS engine. I can hear it spark knocking while driving down the road. Bad gas? Intake gaskets? The whole truck only has 50K miles on it. Yes im sure its spark knocking. I can clearly hear it. Any ideas?
The truck is all stock.

01ssreda4

iTrader: (96)

Is it throwing a misfire code? Or any codes for that matter?

tennerv8

iTrader: (7)

No check engine light. I switched gas brands and i can still hear it.

patSS/00

iTrader: (6)

Lots of possibilities on the LS1, such as:
sucking oil thru the PCV (try a catch can)
carbon build-up in cylinders (related to oil burning)
vacuum leak
maf gone bad or just dirty
EGR bad, if you have one (but should set a code)
O2 bad (also should set a code)
just crappy gas where you are
descreened maf (put screen back)

You should get the codes read, they don't always set an SES light.

camarodude87

iTrader: (8)

What type of gas are you using, I was using regular unleaded and i got spark knock like a ****.. went to premium and the knock was gone, Id try this before anything. but this was in my 83 356 Camaro

tennerv8

iTrader: (7)

I don't want to run premium gas in this thing. Its a bone stock '99 sierra. The whole truck only has 50K on it. Its like brand new. If I put premium in it then im just going around the problem. I was thinking maybe it was a bad intake gasket and it was sucking extra air and making it spark knock. I had this problem on a mid '90's 350 tbi.

It seems there are too many variables here. I know most gas is way lower quality now with the ethanol in it.