For a while now I've had kind of a low hum coming from somewhere in the engine compartment. It varies with engine speed, but I don't hear it much above 1000 rpm or so. (There's a long thread here about an engine drone, but I think I have that too, and this isn't it.) I've been chasing it with a stethoscope, and it seems like it's loudest when I put it on the 2 and 4 injectors. It also sounds like it's everywhere on the fuel rail, but it's not as loud on the 6 injector. I can also hear each injector opening, and they all sound pretty consistent. Plus, I don't have any performance issues that might suggest bad injectors.

Do injectors have anything in them that can hum, especially if they're going bad? Or is there something else in the fuel system that's being transmitted through the fuel rails and the injectors?

Or do I just need to quit worrying and try to teach them all to hum in harmony?

 

Injectors let the gas into the engine by means of a valve operated by an electromagnet (solenoid) so I suppose it would be possible for the injector to make noise. But maybe the fuel itself is "pulsing" in the rail because of the fuel pressure regulator. Just guessing.