Re: 99 Explorer Humming noise
I have found my problem (IAC valve) and I decided to post my findings and forward the info I got:
The sound is called "Moosing" which is caused by the IAC valve. It will resonate throughout the throttlebody/intake making it sound like it is coming from the MAF or airbox or everywhere.
You may need to clean or even replaced the valve.One quick way to find out is to pop off the small black cap on the IAC, all that is, is a small air filter, if that is clogged, it will produce the moosing sound I was hearing.
I have heard brand new IAC's do this from sitting on a shelf and collecting dust and also by making my new one do the same thing by taking off the "cap" and putting my finger over the hole ( was for demonstration purposes for a friend with a ford, he didn't believe me when I told him it could sound like a dying goose! )