Just take the resonator all the way off and inspect it. It could contain the carcass of some rodent that picked the wrong place to build a nest. Drive the car without the box and see how it sounds.
I should probably do that first. It sounds kind of gross if there used to be something alive in there.
My wife thinks that the engine is dying, but just at idle I could hear the noise coming straight from the resonator. I still don't know exactly what it does. I know that it's the air intake, but I've had other cars where the resonator (which I still don't quite understand) was built into the air filter box/case.
OK I looked up what it does. I don't know much about pressure wave harmonics, but apparently it's needed for performance reasons.
Re: 2002 Civic LX - noise from intake resonator
#4708364 03/27/1809:45 AM03/27/1809:45 AM
Follow up. Turns out it was the transmission. I was able to drive it home the next day. Later when I tried to drive it just a little bit it would move a bit and then refuse to move. So it just sat there until I could figure out a better plan.
I brought it to a mechanic I know to have an evaluation. When I checked with my code reader there was no active trouble code about a month ago. It's also been sitting on my driveway for months with maybe one attempt to charge the battery (used an extension cord) but it was pretty dead. Once I connected the charger the alarm goes off, and the remote seems to have a dead battery too. So I'm off to an auto parts store to buy an overpriced A27 so the neighbors don't complain, and I wasn't sure if I could even start it without turning off the alarm. So maybe 45 minutes of charging at 12 A and I can easily start it.
But I basically had to limp that thing about 3 miles. I could get it to move, but eventually it would stop moving and the service engine light went on. The engine seemed fine, but it just won't move. I'd let it cool for a couple of minutes, and I could limp it maybe 3 more blocks at a time.
I get it to him, he notices it barely moves, and he gets his code reader (a really nice one better than mine that only gives code number). It said something about "improper gear ratio". He says "You need a transmission". Asked him what he suggested, and it was to get a rebuilt or used transmission in there. Recommended rebuilt though for a longer warranty and I suppose because they're actually inspected and have worn parts replaced. A local engine/transmission specialist had a rebuilt for $1050+tax, and the mechanic charged about $500 for labor. Other than this and some cosmetic damage the car runs fine. So we've got the car back.