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2007 Camry exhaust buzzing when accelerating

Hello all. I was hoping for a little insight into a slight issue I have.

I have a 2007 Camry le 4 cylinder. When under a load on the highway there is an occasional buzzing that occurs when accelerating (sounds like a piece of metal vibrating at a high pitch). It only happens under about 3000 RPMs and the noise doesn’t occur any other time (idle, reving the engine while idle, slow speeds, etc.). Today I got it up on a lift and checked all of the heat shields under the hood and around the exhaust under the car. Nothing seemed loose. I had two mechanics look at it and one thinks that the exhaust flex pipe is the culprit, while the other insists that this is a known issue with the resonator (said a small piece may have broken off of a baffle inside and is vibrating). Are either of these components well known to cause this type of issue? I’d rather not replace both if one is frequently the cause.

Thanks for any advice.

Is it coming from under the car? Does it sound like it’s coming from the engine area? Is it coming from the back? Can you duplicate it on jack stands?

Can’t replicate the noise on the lift, only on the highway above 55 mph. That is why I think it is likely something involving the exhaust when the car is under load. It sounds like it is coming from the engine area but the exhaust flex pipe connects underneath in front of the drivers seat near the engine compartment. Given that it only happens on the highway it is hard to pinpoint the exact location. I don’t know enough about resonators to say whether the sound would travel if the resonator was the cause or if it would be localized to that exact area.

Have you tried wrapping on the pipes, cat and resonator to see if you can hear the rattle. Also, look at the exhaust manifold and see if there is any discloration around the flange. This would indicate a leak.