Engine bay buzz at 3k rpm?

[CrankyOldMan]

I've noticed recently that when I'm coasting to a stop and my RPMs are over 3K, a strange buzzing noise comes from the engine bay when the tach passes 3K. Has anyone else had this happen before? I'm planning on having someone gently rev the engine while I poke my head under the hood to target it, but it may take a while for the weather to cooperate enough to do that.

[mattymo]

Having same problem around 4000rpm. Lighter or harder throttle seems to affect it. Anyone diagnosed this one?

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[CTScott]

Having same problem around 4000rpm. Lighter or harder throttle seems to affect it. Anyone diagnosed this one?

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Is the AC on when it happens?

[mattymo]

Nope. Happens with or without the compressor on just the same. Sounds like buzzing/grinding sound. Almost sounds like a heat shield vibrating. I hope it's a sheet metal resonance, and not an internal engine sound. For me it seems to happen worse at a "medium" throttle position I like to drive at, as the rpms sweep to 4000 or so. If I give it more or less throttle, the noise doesn't seem as intense.

[ex-x-fire]

There have been complaints about vibrations on some cars I work on, like a ford focus. We find the there's a bad motor mount that sags causing metal to metal contact at certain engine speeds, revving it up make it better or worse.

[John Lenin]

My Yaris is a 2009 2-Dr. H/B, auto-tranny and at a stop with trans in "D", holding car with brake, I have an audible "rattle" as engine idles ... have isolated it to the air filter box (front driver's side under hood) ... apparently this is not uncommon ... either filter box itself is loose or the snorkel attached to it ... will attempt a fix in the spring when the weather gets warmer ...

[bairjo]

Always remember, it doesn't matter if you have an Engine bay buzz or San Franciso Bay buzz going on....never drive buzzed...you may find yourself in a situation...