Funny intake sound at VTEC RPMs

[nsx2tall]

In 2nd gear around 6000+ RPMs, there is the strangest sound coming from my intake. It sounds rather like small pebbles getting kicked up into the wheel well, which is what I thought it was at first. But it happens every time I hit high RPM in 2nd. Obviously I haven't tried it in third because then I go to jail. :frown:

Any thoughts? Should I just take apart the intake and look inside or does anybody have an idea what it might be?

 

[HYPERTUNE]

Sounds like it might be pinging. Did it start happening after you filled up with fuel?

 

[nsx2tall]

Not that I noticed, but I'll keep it in mind-- I hadn't thought of that. I usually use BP 93, where would I go from there?

 

[HYPERTUNE]

Does the noise only happen under load?

The way you are describing the sound really makes me think it is pinging. For that to happen, either you have bad fuel, or something is making the timing advance more than usual. The crank trigger is not adjustable on the NSX, so nothing could have slipped there. Other than that, possibly a faulty sensor?

Do you have a reputable mechanic you can take the car to? Preferably a performance oriented shop that does tuning. If it is pinging they will pick it up right away.

One way that might show if it is knocking is to put a reputable brand of octane booster in it. If you notice that the sound is gone, or at least reduced, you know it is knocking.

 

[nsx2tall]

It had the timing belt, harmonic balancer, and clutch done last fall and about 750 miles ago. If AoB didn't do it exactly right, I'm not sure who would have.

The funny sound occurs only under load-- 6k or higher. This last tank is Shell 93 so maybe something different will happen. Wouldn't the knock sensor throw a CEL code if that is what it was?

When I get some time I'm going to check the intake as well just to be sure.