Morning all,
just noticed the past few days (after my battery die), there is a low growling/grinding noise whenever I do a hard acceleration as soon as I hit 3k rpm...once above that, I cant hear it anymore. There is none of that strange sound if I park and hit the rev, only during driving. I checked all vacuum lines, anything might be loose and couldn't find any. Anyone has experience this?

 

Which engine do you have?

 

It's a 4 cylinder engine.

 

just noticed last night that the noise appear after 3k rpm and stay past it. Didn't notice it until last night when it was quiet and nobody was on the road.

 

ah, found the source...it came from the air box. I replaced my old filter to Fram brand so I switched back to the same brand I been using and it went away.