I just purchased and installed a Stillen Cold Air Box, Stillen Z-tube, and MD 5/16 ISO plenum spacer for my 04' G35 Coupe. Since install at around 2300-2700rpm's i get a loud shriek from what sounds like the intake(vacuum leak). I have taken the whole setup back out to look for problems and found none. Everything was torqued correctly, the rubber ring around the oil filler wasn't pinched, the pcv hose does not appear to be kinked, and im about out of ideas. I have checked and rechecked everything and i cannot get rid of this noise. Does anyone else have any further suggestions? I'm getting really pist off and would really like to shove the parts up their respective makers butts if i can't get this resolved.

 

dont know what the problem could be, but i could buy the plenum spacer if you wouldnt like it nemore

 

Process of elimination. Return everything back to stock piece by piece checking for the noise as you go. I'd start with the airbox and work your way back to the motor.

 

I'm sure that helped solve the problem.

Sorry but some replys get me sometimes...lol

If you have tried everything, and I mean everything (which it seems you already have), I would (if it were me) take the entire setup out. Take it step by step and re-install, taking your time to look over everything twice or even three times before moving on to the next install. This I know is extremely rash and time consuming, but it's the only one true way to find the problem.

You could even take it all back down to stock (think someone mentioned this above in a comment already..?) and then start back from scratch.

Anyone else with these mod's (combo) have any better ideas?

-WoW

 

Check your intake tube and make sure that everything is tight at the MAF sensor, Throttle Body and the emissions tube.

Did you reuse the rubber gasket, which was between the MAF and stock air box? Was the K&N filter properly tightened onto the Hi-Flow ring? Just a couple of things to check. I am sure that you have checked these items more than once. Good luck!

 

If you are talking about the whistling sound you get from the intake under mid throttle, that is absolutely normal. I get the sound all the time, now if you are referring to a different noise, I would start by putting the stock box back on and then see what happens. If that doesn't fix the problem, then spacer needs to come off. I have the pop charger, z tube and just installed the spacer. I don't getting any type of noise other than the whistling sound, but it is very brief.

 

The whistling sound at mid throttle is not normal for me. I have the same mods...Stillen CAI, Z tube, and 5/16 spacer, and I've never had a whistling sound of any type at any rpm. Just a nice, aggressive, growl.

 

The whistling noise is supposed to be normal with the spacer because of the increased volume inside the manifold.

 

Even if you have the spacer or not, with the intake you will hear a hissing sound for sure. That is normal, I even get that with my k&n drop in filter with ztube.

 

lol

 

If you're sure about the torquing....
Check all the hoses & clamps.

I changed out some of the OEM spring clips to hose clamps.
The OEM spring clamps can get weak after being pulled off.

 

Other than a short and slight hissing sound at the throttle body when I blip the throttle at idle, I hear no whistling sounds with my set-up at any rpm range.

 

What im hearing is not the normal short whistle, like when my car was stock. If im in 4th or 5th gear and i am in that 2300-2700rpm range i can make the whistle last for 5+ seconds with light to medium throttle input. What im hearing i have a hard to believing is normal. So i guess im gonna take everything off and add it back one by one. I'm kind of starting to think its not a vacuum leak from the spacer because it seems it would go away when the manifold got hot, but this noise still remains even after driving the car for over an hour. Does anyone else have the Stillen Z tube?

 

can you just remove the spacer and try again? I have Stillen CAI/OEM z tube installed an no issues. Hard to believe it is those that are causing this...

 

My Stillen CAI doesn't but some people have reported that they can indeed whistle.

I doubt it is the spacer because if you had a leak so bad that it cause a whistling sound, your engine would idle obviously rough. A whistle leak is usually a big leak cause by a hose not being plugged in or the oil fill spout being caught in the plenum. ...but you don't have that so it suggests you may be hearing the CAI.

For your first experiment, try removing the CAI and see if it goes away. If it does, then what you hear is only noise and nothing else. If it is still there, you can take off the spacer to see what that does.

In any case, its probably something really simple.