Howling sound coming from intake

[nutcase2be]

Hello all, I am new to posting although I have gleaned greatly from the threads I have read on here. I have a 2000 Ranger XLT 4X4 with a 4.0l A/T. I purchased the truck some six weeks ago, and now that it has warmed up outside I have a howling sound coming from the intake ( I forgot to mention that A K&N cold air intake has been added to this truck). I took the K&N filter off and the howl continued. I took the MASS airflow sensor off and the howling continued. When the A/C Compressor kicks in the howling lessens, but is still there. Anyone ever experienced this before, have any ideas. Thanks

[Davescort97]

How does it run? Possible vacuum leak.

[nutcase2be]

Seems to run just fine. Beside the sound you wouldn't know anything was wrong.

[Davescort97]

Welcome to AF!

The howling sound under acceleration is normal for an engine that has a performance filter on it or no filter at all. It is the sound of the valves sucking air into the cylinders. There is nothing wrong. It's supposed to be that way. The reason you can't hear it on most cars is because the stock air filter uses a silencer box. Feel all that power with a throaty roar--as they say.

[nutcase2be]

The howling sound is at idle and slightly above. It is not the intake simply breathing. I guess some people would get the sound of a breathing engine confused with a potential problem.

[Polymath]

My 1998 Ranger 4.0 is doing that (howling at idle), with the stock air cleaner. Lift the air intake off of the air filter and it's REALLY LOUD. This is at idle, and an on-and-off problem. Something is causing the air intake tube to resonate like an organ pipe at a certain idle speed.

I see several people referring to this as "a howling sound" on wikianswers dot com. Someone claimed that replacing the idle air control fixed it. That is possible, if changing the IAC changed the idle speed slightly.

I have just removed and examined the air intake hose. I see that it is designed with accordion pleats or corrugations at the elbow where it connects to the throttle body. I feel certain that the grooves on the inside of the elbow cause the organ-pipe effect at a certain airflow (a specific idle speed). There are aftermarket improved air-intake hoses with smooth elbows which should fix the problem. I intend to get one.

On my truck the sound is so strong I can feel the air intake hose vibrate. I am concerned that the vibration could eventually cause damage to the throttle body or IAC. Other than that possibility, I believe this to be a harmless eccentricity of the air hose design, that it just does that sometimes.

[Davescort97]

Welcome to AF.

Thank you for clearing that up for us. I was in error.

[highflyer100]

Hello all, this problem sounds very similar to the moosing sound problem Mercury Mystique's and Ford Contour's had. The fix for those vehicles was a redesigned IAC valve. I had one that had the moosing problem and it was very loud. New IAC fixed it, never heard the sound again. Good luck!

[markdpro]

This post saved me at least $300 as I was about to replace the Mass Aairflow sensor. The howl was the Idle control solenoid vibrating. a clean up with some intake cleaner after removing the solenoid fixed the problem. The idle air duct , the small tube parallel and in the air intake hose acts like a trumpet. mooooaaannn.
Nice work people!