Originally Posted by SteveSS
Our gas PM has developed an intermittent low-frequency buzz, sort of like metal vibrating. It seems to be coming from the engine area. It mainly happens under load with light throttle. It goes away when you take your foot off the gas, or give it more gas. Anyone recognize this, or have ideas?
Can you replicate it when stationary and revving? Or must you be on the road?
I have yet another kooky idea which I haven't tried because there hasn't yet been a need for it: get a device that can accept a microphone and that you can listen to what the mike "hears" via headphones. Now move the mike around until the sound gets louder. Where it's loudest is where the sound comes from. However, you can't do it while driving...
The reason I thought of this is actually PM-related. There was a fellow who had a PM and the rear springs squeaked like crazy. The dealer couldn't pinpoint it. If I remember, the dealer fought him on it, claiming it's "normal". I think the owner eventually posted a video on twitter and that might have got him the attention needed to get things going on the warranty repair. --a literal "squeaky wheel" scenario!
I feel that my technique could zero in on the location *exactly*. Because the sound level as heard by the mic would go through the roof as you got near the source of it.
[My guess for the squeaky spring guy was a spring bushing but it's hard to nail down the location because sounds reverberate everywhere.]
The reason I haven't needed to do this yet is that my PM's springs don't squeak--yet. But I think I heard them start to squeak just once. But it's not doing it right now.
As for devices to do this, I think higher end cameras with mic inputs could work, video cameras too if you've got one. Wondering out loud, maybe even 2 cell phones. Call one from the other and use that other one as a microphone that you can wave around.