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98 Ford Ranger Air Intake Howl

Hello to All!

We have a '98 Ford Ranger (4.0L V6, auto. transmission, 74,000 miles). Over the years it has developed a “howl” that comes from the air intake system. The howl starts when the engine is warm, and causes the air filter box and hose connecting the air filter box to the engine to vibrate/resonate. The howl is really noticeable to people nearby and can be heard inside the passenger compartment.

Any thoughts on where to start to quiet this thing down?

Thank you in advance for your response!


The only way for an intake system to develop a howl over time is for either a part of the ducting to become loose or for a secondary air passage into the ductwork to develop, perhaps due to changing of the fit of the plastic pieces, likely at one of the joints.

Sorry, but you’ll need to get your head under the hood, find the source, and secure the part and/or joint.

Thank you for your reply. I had checked fittings in the past, but went “back under the hood” this afternoon.

To make a long story short, the engine will run (and still howls) with the air intake hose removed, so it’s not a problem with the hose/MAF/filter box and/or hose clamps. The sound seems to be coming from the throttle body or intake components after the throttle body. The sound comes through the throttle body.

There seems to be a hard plastic intake “tower” on this engine after the throttle body. I had to have a similar part replaced on my 2000 Ford Explorer (4.0L V6) because it would not idle on start-up in cold weather. Should I be suspicious of this part on the Ranger? Pulling it off will likely be a bit of a job, but do-able. Or are there specific parts in the intake chain that may be likely to resonate (perhaps as they age)?

I appreciate your insights.


I could always tell when my neighbor was pulling into his driveway by the sound of his moaning idle air control valve/IAC.

It’s a common problem and you’ll find the IAC on the passenger side of the throttle body. Remove the 2 wire connector & 2 mounting screws.


You were right on! I looked on the internet for idle air control valve and found many, many posts about noise from air intake systems on this and other Ford engines. The IAC was almost always found to be the culprit.

This morning I bought a replacement IAC at an auto parts store ($51 and change) and put it on. The howl is gone.

Thank you for your insight. And thanks to NPR for hosting this forum.


Good deal & congrats on the fix. Glad I could help.