Hi all, I put a aluminum K&N cold air inlet tube system on my 02 4.6l f150 last summer. over the winter the pipe started making a loud "thunk" sound. At first it sounded like the rearend but now i know its maybe the air idle control valve. With the hood open you can hear it cycle and the aluminum tube breifly resonate like a trumpet with and accompanying woosh of air afterward... seems to cycle with the A/C cycleing. I temporily solved the problem by pinching the large rubber hose going from the inlet tube to the valve just below the AIC motor. The noise stopped and just a little whistle is left.

My question is... what could be the problem? Is it the AIC motor? or another component? can i jerry rig it? or clean something to fix it? any suggestions would be appreciated!

 

I read another thread... the "horn" sound is a bad IAC valve. I havent taken a newer ford apart before at all so let the learnin begin.

Will pinching the hose damage anything? I must drive 1300 miles to florida on friday and cannot replace it before i go. or maybe just unpinch it and let it start quacking again and driving me nuts!

 

It needs air to function. This is why the stock air intake has a silencer to eliminate these noises. I would deal with the noise until you can replace the IAC. 2 8mm bolts and 1 plug. 5 minute job.

 

Update: After driving around for a few days with the vacuum line pinched almost closed... (it did idle funny). I unpinched it and then drove 1500 miles to miami and guess what... the sound never came back and the engine runs great! I'm not sure how or why but i'll take it. Thanks for the reply! :-)