[s-cars] Idle stabalizer valve (ISV) - how does it work?

[chris chambers]

Mike,

is there anyway to test it?

Thanks
Chris


--- Mike Fitton <rfitton at vt.edu> wrote:

> Someone correct me if I'm wrong, but my understanding is this:
> 
> Pneumatically, the ISV sits in the intake system with one side
> hooking 
> up before the throttle and the other side hooking up after the 
> throttle.  Airflow is controlled by a rotating valve operated by a 
> solenoid.  When the throttle position sensor tells the ECU that the 
> throttle is at or near fully closed, the ISV circuit becomes eligible
> 
> for operation.  The ECU pulses the solenoid on a duty cycle, I
> assumed 
> timed to coincide with each cylinder's intake stroke.  Near the time 
> when a piston begins moving down on intake, ECU opens the valve
> allowing 
> intake air to bypass the throttle plate.  By precisely timing the 
> operation of the valve, the ECU is able to deliver precisely the
> amount 
> of air required to sustain the exact idle speed.  Of course it's
> still 
> dealing with the whole gasoline side of things simultaneously and to
> the 
> same end.
> 
> That's the quick and dirty.  Can't tell you anything about exact
> timings 
> of the cycling or whether or not it cares about crank position during
> 
> all this, nor any good data on the ramp profile of the airflow due to
> 
> such rapid cycling.
> 
> -Cheers!
> Mike
> 
> chris chambers wrote:
> > Gentz,
> >
> > Previously the car's idle would "pulse" up and down, I cleaned the
> > ISV with carb cleaner and it idled better but not "right".
> >
> > Apparently I have a defective ISV, wondering how it works.
> > With the ISV's wires plugged in the car won't idle and dies when
> > the throttle isn't pressed. Unplug the ISV's wire and the car idles
> but
> > I get a check engine light.
> >
> > Nothing else was unplugged on the engine, I know some people have
> > plugged a different cable in to the ISV and the car ran bad, this
> > isn't the case.
> >
> > Is the ISV servicable or does it need to be replaced?
> >
> > Make April 15th just another day http://www.fairtax.org
> >
> >
> >
> >       
> > _______________________________________________
> > S-CAR-List mailing list
> > S-CAR-List at audifans.com
> > http://www.audifans.com/mailman/listinfo/s-car-list
> >
> >   
> 
> 


Make April 15th just another day http://www.fairtax.org