im getting a loud whistle that starts slowly, when i turn on when warming up and dies when rpms settle, but comes back at 1000 and gets louder the higher the rpms get, thought it could be loose spark plug, checked and all are tight, no noticeable loose or disconnected vacuum hoses, please any insight would help this is my daily driver, but in this condition ...well...its not
1996 F-150 215K mi, brand new K&N FIPK

 

Two questions:
1....is it a high pitched whistle, or more of just a loud sucking sound?

2. Was it there before you put on the FIPK?

 

my K&N cold air intake on my jeep made a high pitch wistle at around 1300 rpm. I know you have it in a ford but i was told open air filters would make that wistling sound, my 96 f-150 has a k&n but it's just a replacement filter...

 

my truck whistles like a turbo.. but its caused by the butterflys in the TB

 

and that's exactly why I asked.....especially with our fords, when you put a free-flowing air intake on it, and an open-element air filter, you do hear a sucking noise when it's cold and as you go up the revs.

What you may be hearing is the all the air for the engine being sucked through the small hole (3/4" maybe?) of the IAC (idle air control) valve. When your foot isn't on the gas pedal, the throttle plates are completely closed, so how does your engine get the air to idle? Its the IAC valve, which is controlled by your computer, that knows your throttle is closed by the readings being sent back by the TPS (throttle position sensor). Anyways, its a small hole, and a large amount of air moving through a small hole at high speed makes a whistling noise.

Easy way to tell, open your hood and listen at the air filter while your engine is running. If it sounds like the "sucking/whistling" noise is coming from the intake, that is most likely your noise and is completely normal.

 

k&N / MAF don't like each other very much, the oil used on the filter likes to get the MAF sensor dirty, wich isn't very nice.

 

yeah definitely high pitched, almost a metal on metal whining sound, but not coming from my pulleys, and definitely not the FIPK you can hear it sucking here and there but not this sound plus different area of engine compartment, and the day it started i drove to and from work, started it up a few hours later to got the px and get gas and thats when it started

 

alternator bearings or the belt tensioner or the idler pulley....

 

Oh, so you're talking left side as in when you're looking at the engine? any you're sure its not from the pulleys? The bearings for the smog pump are pretty famous for going out

 

with a sound this loud it a little hard to tell but sounds deep on the left (as your looking at it) side of the engine which is what made me suspect maybe it was a loose spark plug, but theyre all good, i dont even know if it could be the seal at the heads but it doesnt sound like the alternator which i got uncomfortably close to while the engine was running to see if i could hear the noise destinctly from it