I have a K&N series 77 intake and a whooping noise has started echoing through the intake. At first it was just when I slowed down to make a turn or something, but now it does it almost every time I let off of the gas. I have cleaned the air filter, the maf sensor, and sprayed intake cleaner in the intake and it still does it. Can anyone help me?

Thanks,

 

I had the same "problem" or symptom last week. It started for no reason. I do not have a K&N filter setup, mine is stock. But, I did hear the same type of sound coming from the engine but, I could not isolate the source. I changed the PCV valve, it was due. I was going to replace the belt since it had 125K on it but, I could not find one that would fit, so I put the old one back on the engine. The old belt looked fine. Now, the noise has gone away. I did remove/reinstall the air cleaner assembly in the process of trying to change the belt. Since I do not know what was causing the noise or why it went away, I do expect it to return.

 

When I installed my K & N Filter a few years back my 97 F-150 developed a loud whhoping noise also. I went back and reinstalled the little black plastic box that was near the throttle body. It acts like a muffler. To get it plumbed in with the K & N I went to NAPA Auto Parts and bought a hose part # 9816 for $10.18 tax included. Had to trip a bit off each end of the hose to get everything back under the throttle body cover.

 

did this stop your problem? Is it the elbow looking piece?

 

Yes it did stop the noise. It is a small plastic box device with a small pipe on each side to take the hose. Not sure what it is called but you most likely had to remove it when you installed the K & N Filter system.

I kept all the old stuff in a box in the garage so was easy to find and reinstall.

 

It was the IAC valve.

 

It's the IAC valve alright !! But it's not bad - That's the purpose of the IAC muffler. That's exactly what it is. They all can get noisy and when they do , that muffler comes into play. That's what it's for.

T Ellenberger did the smart thing

 

Maybe OT but my wife's 02 Mustang GT makes the same kind of noise out of the intake tube behind the airfilter. Sounds like something fluttering in the tube somewhere. Completely stock.

Think it could be the same kind of thing?

Thanks!

 

Yea , anytime you bolt on an after market air intake you going to get induction noise - Like the old 4 barrel carburetor sound. That's normal when you consider the factory intake is chambered and designed to eliminate most of that.

The IAC's get noisy with age and the aftermarket intake systems do not test their systems with an older IAC component and most likely don't warn you about this possible problem.

The better IAC, plenum and muffler set up IMO is on the older 5.4's and the newer 4.6L's.

The IAC is bolted on the rear of the plenum back by the firewall and uses a in-line round IAC muffler vrs's the rectangled one on setups with the IAC bolted to the side of the plenum, toward the front.

The in-line IAC muffler set up -




The 4.6L box type is here -

http://www.fordf150.net/howto/throttlebodyclean.php