VALVE ASSY, VACUUM SWITCHING, what's this for ?

[Uzelac]

part number is 89570‑12290

Don't know the use of it, looks like engine is runing fine with and without it.

Thanks

[banpei]

I'm sorry but I can't find that part in my EPC. Any more details where it is located?

[Jonny Rochester]

Is is called a VSV, or vacuum switching valve. I think it switches sometimes to idle the motor up, maybe when the A/C is running. I can't be sure.

[parrot]

You need to post a pic up

[Uzelac]

The most left thing on picuture.

One more:

[Uzelac]

Obviusly made error on qouting part.

Real PN is
17650-89570‑12290

[parrot]

Yes it is a generic idle up VSV. It will only work if you have a GT spec charge/lights loom and GT spec underdash loom. in other words a functioning idle up circuit.

As you can see, one vacuum line goes to the throttle body to sense when the engine is at idle, the other outlet goes to the airfilter i.e. atmosphere.

Edit: there is another idle up vsv used when the vehicle has aircon which mounts on the right strut tower, at least on RHD cars.

[Uzelac]

No lights, no a/c no p/s.
Taken off, no problems.

Thanks

[kawo]

I hope I understand how the VSV work and according to the manual, the VSV should turn off after 10 seconds from startup of engine.

However, I keep hearing very loud hissing sound from the VSV. It seems it is always on? It seems that some electric devices is keeping it open all the time? How should I diagnostic this problem? Will this strange VSV behavior lead to a jumpy idle(which is intermittent at red-light and looks like you did not bleed the coolant)? Will this strange VSV behavior lead to engine check light when I floor the gas?

[jondee86]

The small VSV pictured above is installed at the factory with one tube
connected to the throttle body and the other tube connected to a source
of filtered air. It will normally raise the idle speed about 100 rpm when
it is active. That is not enough air to cause rough or loping idle.

According to the actual model of your car, the idle-up VSV can be active
when one or more of the following occur...
- at engine start up
- when head lights are ON
- when brake lights are ON
- when rear screen heater is ON
- when heater fan is ON
- when A/C is ON (some cars have a separate VSV for A/C).

There is no fault code for the VSV so it is most unlikely that it can cause
the check engine light to come on. Loping idle is almost always caused
by a blocked thermostatic idle-up valve, or a vacuum leak that raises
the idle speed high enough to initiate fuel cut (>1700 rpm).

Cheers... jondee86