I just bought a K&N FIPK system for my 01 F 150/5.4 and now theres a hissing sound coming from the intake. I've checked everything making sure it was tight and made sure it was on right. Does anyone have this same problem and how to stop it?

 

I have the same intake on my 2000 F150 5.4 It's the FIPK II. When I have the hood open I notice that same kind of louder hissy type sound, but its not noticeable at all when I have the hood down. Of course when I drive you hear the intake suck in air and its louder than the stock system, but I believe thats completely normal. What you're describing seems to be the same sort of thing? Plus i know for a fact there are no leaks on mine or any problems. I think its normal.

 

You may be hearing the IAC bypass air. usually it is more noticable when the truck is cold. the IAC lets less air past the throttle body when the engine is warm so you dont hear as much hiss. many aftermarket intakes on many vehicles both import and domestic make this sound.

 

Cool thanks for the help guys

 

i hate to say it, but it is called the noise air makes when it goes through an intake. you can actually hear it because A: it is not so restricted B: it also exposed instead of muffled by all the plastic tubing. hope this helps beware of amatuers they have alot of bad advice.

 

one more thing that is why you change intakes so that it gets more air.