Strange noise/vibration under heavy engine load
 

The latest strange noise coming from my BRZ crops up while accelerating hard between 4k - 5.5k RPMs. It's a hard noise to describe, but it sounds like a combination of spring peeper frogs (not crickets) and a dial-up modem. Again, this only happens when the engine is under heavy load. It doesn't happen during normal driving/acceleration.

Any idea what might be causing this?

My first thought is that it might have something to do with the port injectors activating around these RMP's, or maybe it's just a vibration in the noise generator. I haven't done the noise generator delete yet, but I'll see if that helps.

could be different but i had a rattle right around the same... took it in and this is whta tehy said was the fix...
http://i46.tinypic.com/2mrf6gj.jpg

so maybe check the torque on the bolts?

ps F and the cause got mixed up cause the dealer i went to is really stupid so pay no mind to that as it was a different issue... its the cause part to pay attention to.

I get a similar rattle/vibration in that RPM range like some metal shield is loose but I haven't bothered to look into it. Been waiting on an exhaust and figured I'd check then.
I am somewhat relieved I'm not the only one.

This sounds like what I have. I have described it as heat shield.

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Engine cover bolts loose. Wonder if they'd fall off if you never botherd about it :O

I have this exact sound, when you floor the throttle around 3krpm upwards theres a strange spring sound coming from behing the steering wheel/noise generator area. I will probably bring it up with the dealer when i go in for a service.

Just an update - I removed my sound tube (and plugged my intake and firewall holes) and that seemed to cure the problem. No more weird noise/vibration. Interesting.

Interesting

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What did you use to plug the ends of the intake noise generator thingy? Seems like a large one at the air box and a smaller one at the firewall.

thank god!! ive been having the same issue only lately tho i thought it was from recent upgrades avo intake tube kit and filter also installed crawford performance a/o separator anyone visit the dealer please let us know what they say im sure if i go in and have them check it they will blame it on upgrades id rather not take everything off and take it in

Yesterday i went for service for an unrelated issue but mentioned this to the mechanic. we took it out for a test drive and he heard the noise and said ooo its normal all 6 speed trannys make that noise..i wanted to knock this dude out when he said that...I told him that he should check the engine cover because other people have had the issue and he said he did before we went on the test drive...what a bs'r..I just want to fix my cel and i guess ill have to do this myself or take it to another service center

Dealership tried to find it. They said they put dine rubber washers on some bolts below on one if the shields. I just need a minute ticket look myself. But I'm going to bring it up again when I bring it in for the chirp part install. The more failed documented issues the better for the lemon law.

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Yes, Rattle under engine load is likely the sound tube
 

I experienced this same problem, a loud rattling sound at moderate to high engine RPM under heavy load.

You cannot reproduce this problem while parked / out of gear. The engine needs to be under load in order to produce the necessary sympathetic vibrations.

After trying to reproduce a number of times while parked (and failing), I took a close look at the engine layout, particularly the sound tube and the intake manifold. You'll notice that the sound tube is mounted with a single bolt, and the intermediate box/chamber thing (to which the mounting apparatus is attached) passes very close to the intake manifold. Plus, there is considerable play in the mount (rubber bushing, etc.) by design. Looking underneath the point where the sound tube apparatus passed over the engine cover, I noticed a small amount of wear (slight discoloration -- slightly white plastic) on the intake manifold -- evidence that something was banging / scraping against it, and there's only one thing it could have been: the sound tube.

I fixed this problem by creating a cushion to prevent the sound tube from banging against the intake manifold. If you look underneath the sound tube mounting arm, you'll see that it is hollow underneath. This spoiled my original plan but enabled a better one. I took a piece of durable rubber of the right width to stick out of the mounting arm and rolled up enough of it to stick into the hole underneath the arm, held in place by friction fit. This allows the sound tube arm to rest on the intake manifold and when the engine is vibrating, it absorbs the shock of those vibrations.

Removing the sound tube, of course, would fix this problem too, but if you don't want to do that, this approach works nicely. I've been running with this buffer in place for well over 1000 miles -- it definitely addressed the high RPM rattle under load, and it hasn't moved a mm since I installed it.

Here is a pic of the bolts that need the washers because the collar is to big. You can access them without lifting the car. Just got some nylon washers from ace.

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