I've got what sounds like a muffler just starting to go bad when I hit 2500 RPM. 03.5 Sedan with 84k miles, I really don't think it is the muffler though. Any ideas on what to look for that may cause a sound like that at 2500 RPM? I've heard it could be a weld gone bad on a heat shield over a cat (vibration) - any other things I could look for? Thanks.

 

Does it sound like vibration or resonance? Is there a maximum RPM range that it occurs, meaning at what point does the sound start/stop?

 

It sounds like resonance to me. It does go down as I increase RPM above 2500, but not sure if the noise really goes down or the engine noise drowns it out more. It definitely does not get worse as I go higher than 2500 RPM though, and if I had to guess I would say it does go down some.

If I punch it from a stop I do not hear it immediately, it is when I get to 2500 RPM that I do.

 

I know this may seem like a weird questions, but what clutch and flywheel are you using. If you are wondering why it matters, the G35 will have a bit of gear noise that is audible as resonance with a lightened flywheel. I just so happen to have a lightened assembly in my car and I have noticed this resonance at the exact same RPM. It is possible that you are hearing this as a result of a dampener break-down in the stock dual-mass flywheel which would reduce its muffeling affect thus leading to resonance.

I know, it could be other things too, but the fact that it developed quickly without any other symptom is a bit strange and ultimately why I suggest the above possible cause.

Onto another possible cause, have you recently run over anything? If so, you could have damaged the exhaust or even caused a heat sheild to be tweeked causing this sound.

 

why are you ruling out the muffler when you say it sounds like the muffler?

It very well could be the muffler. I know people that have had them go bad.

 

Perhaps you must have missunderstood, I wasn't saying that it coundn't be the muffler, I was just providing other possible causes. No harm, no foul....

 

Check the B-Pipe to Muffler connection gasket.

 

I think his comment was directed at me. I don't think it's the muffler because I've had mufflers go bad on other cars before, and it didn't behave like this (only at 2500 RPM). After listening more closely, it definitely gets better (less noisy) above 2500 RPM.

100% stock sedan, AT.

I'll have a look at things under the car this weekend, if it's not a total washout like it's supposed to be here. I have a feeling it will either be a heat shield or one of the connection points (along AARONHL's suggestion).

Thanks guys.

 

Bring it by my place, i can take a look at it for you.

 

Do you have any sound clips we can hear so we can help diagnose the problem for you?

 

I just purchased an 03 Sedan, no mods, 76K, and I have the same resonating sound at 2500 rpm.

Jim, if you find out, please let me know.