98' SOHC- Intake Manifold Tuning hisssssss. How do I stop it? (pic included)

[ak74]

Like the title says- I have a 98 SOHC and under heavy (over 3k rpm) acceleration, the intake manifold tuning valve lets out a loud, high pitched hiss. When I ease off the gas, the hiss will continue until I let off the throttle completely.

Here's a picture of the intake manifold tuning device in question:

While the car is idling, I can open the valve manually and hear the hiss (though it's not as loud as when I am accelerating).

My question- is there anything I can do to stop this? Can I spray some lube in the opening or something? There's a vacuum line that connects to the unit and I've driven with it attached and unattached with identical results.

Thanks in advance!

 

[jhclance]

Sounds to me like it is leaking, so i would say replace said valve

 

[my98nnj]

While the car is idling, I can open the valve manually and hear the hiss (though it's not as loud as when I am accelerating).

There's a vacuum line that connects to the unit and I've driven with it attached and unattached with identical results.

Those two statements make me wonder....

If you manually activate the valve and hear the hiss, then how in the world can you also hear the hiss when the vacuum line is disconnected from it, disableing it?

That leads me to believe the the valve is not the cause of your hiss.

That valve changes the intake path during higher RPM's. When the vacuum is disconnected from it, the intake path doesn't change. So where's the hiss really coming from?

 

[Van]

For 4 years now I have heard a "hiss" coming from the engine compartment.
No one has ever been able to locate it.
Very mysterious.
I hope someone can shed light on this.

 

[2000StreetRod]

VIS vacuum motor diaphragm

Some of the 97 and 98 SOHC v6s were equipped with a variable intake system (VIS). The intake manifold incorporates variable length intake runnners that are controlled by the vacuum motor circled in the photo. A PCM controlled solenoid activates the vacuum motor above 3000 rpm. The diaphragm in the vacuum motor may be ruptured. You can check it with a hand vacuum pump connected to the vacuum port. If it doesn't hold vacuum then it needs to be replaced. Also, disconnect the actuator rod and make sure the lever rotates freely. Residue builds up in the manifold impeding the intake runner control movement.