Well, this has been going on for a while, its a SOHC ZC, when the car is idling you can hear loud *** hissing from the IM it sounds like a vacuum cleaner, is this normal for a car with an aftermarket CAI? its a loud *** rush of air, last night when I was parked inside the carwash and the car was idling with the hood open, I could hear the suction from 4 booths away, its kinda embarasing because people often think there is something wrong with my engine, it runs fine for 380,000 kilomiters but I would love to know how that noise is being made.

 

Is it an aftermarket intake manifold or the cold air intake? Could possibly be the intake manifold gasket leaking. But if your reffering to the cold air intake then yes they do make a strange almost whining sound. Some do anyway.

 

mines that big sylicone one, the thing is I had it on other honda's of mine, and I never had this problem. could be a bad gasket since the car runs like ---- sometimes.

 

Spray some carb cleaner or something around the IM gasket area and if you hear a noticable change in the idle, it's safe to assume your gasket is leaking. Just do this when it's not hot or else you'll have a slight explosion

 

Ok I took a closer look, the noise is not coming from the IM seal area, but from the filter, if I take off the intake pipe then its coming from inside the Intake Manifold, like inside of it where the runners are, I have no clue what is making that noise but it bugs the hell out of me because its a loud constant hiss.

 

Go record the sound

 

its perfectly fine, i put on some regular exhaust pipe and a k&n and it hissed, it even sounded like a whistle at WOT from outside the car.

 

agreed, but the whistle that most people hear are from the intake are from the idle adjustment screw.

 

stick a sock in there.