2000 LS engine knocking!

[krislake]

I,m going to try to make a long story short. I bought this car from a lady that used to live in my neighborhood. She told me the engine was locked up. after sitting in my driveway for several months I got it running. It was not locked up, I think it was hydrolocked. Anyway Ive been driving it around a little lately, and this afternoon the right bank started knocking when started it. If you feather the gas you can still hear it ever when the rpms go down. Does not knock if under a load as far I can tell. Does this sound like piston slap, timing chain tensioner, injector, bad gas. Don't know where to start. Any help would be appreciated. Look forward to hearing something, and helping any body else with issues if I can. I'm sorry this is a 3.0L V6

[shorod]

Welcome to the forum!

Have you changed the oil and filter since getting it? Could it be you are experiencing a misfire rather than a knocking?

-Rod

[krislake]

Yes I did, could a missfire cause this engine noise? I've heard missfire in diesels sound like this but not in a gas engine, the check engine light came on soon after the misfire. But I left my obdII in my toolbox at work and could not check DTCs. I just had a sick feeling when I heard the knock, all I could think about was a spun rod bearing

[shorod]

Since I'm not able to hear the noise, I don't know if a misfire could sound like what you're experiencing. However, misfires are pretty common on this generation of LS, and sometimes misfires will seem to disappear as the engine speed increases. Since the CEL illuminated, you will definitely want to pull the codes before worrying too much about a spun rod bearing. If you have a P0301, P0302, through P0306, you have a misfire.

-Rod

[gcwimmer]

I hope you are using 91+ grade gasoline.

You might want to try Sea Foam to clear out any carbon/sludge build up.

[shorod]

That is a good suggestion. Lower octane could cause pre-detonation. Carbon build up could contribute to misfiring. Using SeaFoam as prescribed for Cylinder DeCarb works wonders!

-Rod