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Loud hissing noise

3452 Views 10 Replies 11 Participants Last post by  Bunkins
Every since I installed my M-1 intake manifold and 14X4 round open air cleaner when I first start the truck I hear a loud hissing noise. Well earlier after I finished up fixing my vacuum lines I noticed that it sounds like it is coming from the front of the intake manifold under the breather. The air cleaner is sitting on the manifold good and tight and there is a gasket there. Is this just normal from the intake and air cleaner?
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Mine does the same thing and has for a while, and I have the stock airbox. Let me know if you figure something out Robert.
i'm pretty sure that's just a normal noise that open element air filters make. mine does it, but only when it's cold outside. once my truck warms up it goes away.
I'm pretty sure its the open element as well...they tend to whistle sometimes
Could just be your throttle body. If you take off your air filter all together, you will notice it hisses very loudly.
it's the AIC valve letting air in to adjust the idle. Perfectly normal, noticed it also when I installed my chrome hat air intake.
You don't usually hear it with the stock box because it muffles the sounds so much.

It should quieted down once the engine warms up or you give it a little gas.

Mine's disconnected so I don't have any hiss :D:
mine does the same thing. really bad at startup, then it kind of goes away a bit.
mine does it also. at least since i installed my round filter. it happens some at startup, then when i hit the skinny pedal. i think its just the air rushing by the throttle blades.
you can spray quick-start aka e-ther near where you hear it.. the engine will rev, if there is a vacume leak.

sounds like a vacume leak.
if its not a vaccuum leak then go to autozone and by an "airfilter mounting gasket" for 2 bucks it fixed mine
Mine does it too, with that ram air hood it sounds like a turbo under boost..

If it keeps doing it even after it's warm, and your idle has increased from normal it's normally the gasket under the TB, or a intake gasket to the head leaking by..

Choppy idle is a vaccum line, sometimes it may not be choppy and your idle will increase a little, but it's normally not loud enough to hear it unless you right up to it..
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