I have been experiencing a sound like metal marbles in a can for about 3 seconds under heavy acceleration, then it goes away. I thought it may be spark knock, so I am going to start using premium. However, I was talking to a guy who said that it could be lifter float for a second or two under accelleration, until the oil pressure got to the lifters. I dont like the idea of my lifters smacking my cam or pre-ignition. Has anybody experienced these symptoms? The sound is pretty loud when it happens, but like I said, its only under load and for a few seconds.

A few notes- I have disconnected the EGR valve and air pump. Would this lend itself to spark-knock? My comp. isn't throwing any codes.

 

It's not "lifter float". There's no such thing.

The lifters don't "smack into" the cam. They're up against it, 100% of the time; the valve springs keep them there.

Oil pressure doesn't "get to" the lifters during acceleration; it's always there.

It's spark knock.

Back your timing off in the smallest possible increments, unitl it quits.