I have a 98 ford explorer sport. When the temp. is warm outside the engine starts to make a humm. It sounds like it is comming from the intake. I was wondering what other people think it might be. I think it might be the intake air flow sensor. No codes and no lights.
The hum (sometimes described as a moan) is *usually* due to the IAC resonating. Replacing the IAC has cured these.
What is the IAC? What does that stand for?
Idle Air Control (valve). Computer controlled valve, allows air to bypass the throttle plate (thus controlling engine idle speed). Takes the place of the screw that used to hold the throttle plate slightly open on the carburetor. If I remember, mine looked something like this
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