Hey I have a 2009 Honda coupe and around 1500 rpm in second or third I get a rattling noise when accelerating. When I let off the gas it takes a second for it to go away or I can accelerate more and the sound disappears. Checked my alternator and it's charging (although not sure if bearing is good), replaced tensioner pully, and my A/C pulley sounds like it is rubbing a little but ok for the most part. Power steering seems fine, no new noises no matter which way I turn. And the serpentine belt was replaced as well. No timing belt in this car either.

Because this noise isn't consistent I'm at a loss on this one.

Besides this noise the car drives fine.

 

Can you duplicate the sound without actually driving? It would be good to pinpoint the location of the sound. Maybe a scrap piece of garden hose up to your ear?

Is it coming from the chain-case? Or from the exhaust manifold? Or somewhere else?

 

@JimBlake As far as I can tell I can't remake the noise without driving although haven't tried as hard to do this. Changing out all of the pieces that I have already did make the sounds a lot less and want to be sure I am going through the right avenues.

As far as I can tell the exhaust manifold seems fine.

The chain case I am unsure of however wouldn't that be more of a consistent sound? I will work on recreating it in the driveway and see if I can hear anything, so far I haven't been able to.

 

Have a trusted helper? Open the hood & have them put it in Drive & hold the brakes real good. See if you can hear it while revving in Drive. Maybe stand to the side & not right in front of the car...
It's not good to brake-torque like that for long, but for the few seconds that it takes to hear the rattling.

I guess I'd agree that a rattling timing chain should vary with RPM - but not change with load. But who knows? The real point is to find the location.

 

Have you checked the items related to the serpentine belt?
Like AC compressor, Alternator, Tensioner, etc.... maybe one or more of the bolts holding them may be loose?

Try putting it in neutral and rev it up to 2500 and see if the noise happens.
Have someone do this and you look at the belt and see if you see it vibrating.

 

Another idea?

Weak or broken engine mount will make the exhaust system rise & fall with the amount of load on the engine. Then a heat shield might rattle against something only when you're accelerating.