I have a 2000 Z28 with almost 82,000 miles on it. When my car idles it makes a very quiet almost unnoticable clicking (I guess that's the best way to describe it) sound from the engine. When I'm driving when it revs to about 2500 RPM under normal acceleration the sound gets louder and sounds more like a mechanical wirring sound. When the car is cold the noise starts at about 2000 and is much louder, the sound goes away somewhat after the car warms up. Also I've been noticing that the sound completely goes away for a while after I fill my tank up, then the noise comes back after the gas needle starts moving. I took it over the an engine rebuilding shop and had them drive it around for a while, they said it could be piston knock caused by short cylinder sleeves but I've never heard of that before. Has anyone experienced this kind of problem before?

 

Could be the infamous piston slap. Are you sure it's not detonating? Pull a couple plugs and check them for white spotting.

 

Lifters.

 

I have a video of it now.

Engine Noise

 

i notice mine does the same thing just when i put it in gear and start to move it gets alil louder than what you can hear on the video clip. a coulp of people on here told me it could be piston slap but after really listing to mine for a while it kinda makes me think it spun a bearing or all of them because it doesnt seem to have as much power as it did when i got it.

 

That's what the shop I took it to yesterday said. When I change the oil there isn't any metal shavings or anything in it. With a spun bearing doesn't the engine die pretty quick? It's been making this sound for a while.

 

Could it possibly be a bad knock sensor?