Date:         Wed, 17 Sep 1997 11:54:00 EDT
Reply-To:     Sean Bartnik <sbart7kb@WWW.MWC.EDU>
Sender:       Vanagon mailing list <Vanagon@Gerry.SDSC.EDU>
From:         Sean Bartnik <sbart7kb@WWW.MWC.EDU>
Subject:      Re: Stalling at Idle when cold
Comments: To: Paul Henderson <pgh@unx.dec.com>
In-Reply-To:  <9709171506.AA16547@fetch.unx.dec.com>; from "Paul Henderson" at
              Sep 17, 97 11:06 am

>
> Sean writes:
> >
> > > Paul writes:
> > > The cold idle circuit of most Bosch fuel injection systems incorporate
> > > an "auxillary air regulator". When you start the engine, this valve is
> > > open, allowing additional air (and hence gas) to be consumed by the
> > > engine.
> > >
> > This is incorrect.  The auxiliary air regulator does NOT allow any more
> > gas into the engine.  It also does NOT change the air/fuel mixture being
> > burned by the engine.
>
> I didn't say it did. I "allow(s) additional air (and hence gas) to be
> consumed". At the higher idle, additional air and gas are consumed.


DOH!  Apology to Paul for putting words in his mouth here.  True he did
not say that the aux. air regulator changes the mixture -- I was in a
hurry typing it and didn't read it carefully.  I thought it might be
construed by others that the aux. air regulator changes the air/fuel
mixture, which is a common misconception.

> >
> > The air/fuel mixture is determined by the computer, which notes how much
> > air, how cold/warm it is, how cold/warm the engine is -- then the
> > computer decides how much fuel to inject by varying the time the
> > injectors are open.  Note that the state of the aux. air regulator has
> > no bearing on how much fuel the computer injects.
>
> I didn't say it had a bearing.

I know, but many people think it does.

> > the auxiliary air regulator itself, though.
>
> The aux. air regulator is simply faking that there is more air
> entering the system than would be based on the throttle setting, and
> thus the idle increases. More air and gas is being consumed at the higher
> idle speed. The engine runs faster, and thus doesn't stall when cold.

Absolutely correct.

>
> The bottom line is that a bad aux. air regulator is often the
> problem when a cold, Bosch FI engine stalls repeatedly.
>
>
Sorry, my fault, I will try to read more carefully before I open my
mouth.

Sean

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