Engine humm when air temp. is worm or hot

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Jarred Jewett - 16 Apr 2005 19:30 GMT

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.

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Jim Warman - 16 Apr 2005 21:30 GMT

The hum (sometimes described as a moan) is *usually* due to the IAC
resonating. Replacing the IAC has cured these.

> 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.

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Jarred Jewett - 17 Apr 2005 00:55 GMT

What is the IAC? What does that stand for?

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Just_Steve - 17 Apr 2005 02:59 GMT

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
http://www.partsamerica.com/product_images/AAP/GPS/A0-AC/AC56.jpg Depending
on your engine, yours might look something like this
http://www.partsamerica.com/product_images/img/NIE/22972.jpg

When mine went bad (actually, when I ruined it by trying to clean it) it
caused my '96 4.0 OHV to sound like a toy horn at idle, sound would go away
when throttle was opened. Real simple to replace, bought mine for about $45
at O'Reilly.

> What is the IAC? What does that stand for?

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