Humming from air intake

My 2000 Crown Victoria has recently started making a humming noise that seems to come from the air intake. It is sort of a high-pitched noise that can be rather loud. The noise does not start until I put the car into gear and will usually die out a few minutes into the trip.

My mechanic thought it was the mass air flow sensor. He replaced the part to no avail. After reading some of the other posts, I am beginning to think it may have something to do with the idle air control valve, transition piece to the throttle body, or the throttle body itself.

Any help on this would be appreciated.

I had a 92 Vic that did the same thing. I also suspected the idle air valve. Ended up trading it on 99 Vic before getting to that prob. The 92 also started idling at erratic speeds which it did prior to replacing the idle air valve the first time about 5 years ago. You could also check the EGR and PVC systems.

Your mechanic was guessing, and guessing wrong. I hope you did not have to pay for his incorrect guess.

As Pat 96 suggested, this is usually (almost always) due to a bad IAC (Idle Air Control) valve, just as with his case. The technical term for it is "trumpeting".

Thanks for the help guys!! I will definitely have the valve looked at. Much appreciated...

W