2.3L LF engine: strange sound at mid-rpm, possibly heatshields?

[AlS]

Hello all. I have a 2006 hatch with 21000 miles on it. Bought used. Noticed a strange sound at about 2900 and 3700-3900 RPMs during acceleration: kind of mild dingling or grinding, maybe mild ringing even. Almost like someone left a wrench somewhere on a metal part inside the hood, and it dzzzzz-ingles a little. Not sure what word would best desribe it. Sort of what you might hear if you had small metal parts loose inside the exhaust system. The sound is pretty quiet, rather a tone-change than an actual "alien" component most of the time, but occasionally gets more 'musical'; can't hear it under rain/wipers, definitely not with music on. It does not reproduce at P or N, only in motion, and only when "going up" the RPM (no matter how much throttle, but you have to have some, going down the RPM there is no sound). If you just hold the pedal steady, there is no sound. At first I thought this may be detonation (knocking, pinging), but it is not the same harmonica, and not that loud. Gear- and gas-independent. Cold or hot.

Put some 91 gas and raced the engine a bit. Performed the "spark-plug cleaning procedure" (3000 RPM for 3 min). Tough luck...

It may be just a component of normal engine sound with stock exhasut, that gets stronger than usual. Dealership claims "they took another car from the lot and it has that too"; suggest it is heatshield vibration. Needless to say those are tightened properly.

I rented a same car and it has that sound at the same RPMs but much weaker.

Any of you have this component? Is this normal?
What can be the source?

Thanks, this is driving me nuts.

[RX9]

i belived that no one onboard can say what coused that sound just by your words. may be just a loose screw, maybe inside the cat is rusted, too many maybes, you better go to dealer check it out.

[Skarbro]

you better go to dealer check it out.

Dealership claims "they took another car from the lot and it has that too"; suggest it is heatshield vibration. Needless to say those are tightened properly.
:)

[AlS]

Yes, two dealerhips were not helpful.

My question though is whether any of you fellows have that. Out of 3 cars tested all 3 had the sound, to a different extent: mine, a rental (much weaker), and a new one from the dealer's lot (taking their word for it). Based on this, a lot of other owners should have that too, and maybe that will help figure out where it is coming from.