[T3] my long term issue have to unplug TS1 for a smooth idle.

William Jahn willjahn975 at gmail.com
Tue Oct 1 10:21:27 PDT 2019


 I just wanted to make sure the AAR rotary valve slot was physically close
to fully open to rule it out as the cause for the low cold start RPM before
I started the car just in case the engine running might jar a stuck closed
valve free.

  Then we will say the AAR is just added air that enters past a closed
throttle which the MPS senses this affect and corrects the mixture based in
the pressure difference in the IAD in turn causes the MPS to make the mix
richer . Yet you said the AAR open or closed , the mixture should be
approximately the same. Does this mean it still does have some affect of
making the mix richer?

  I thought if the AAR is wide open and you place your thumb over the hose
removed from the oil bath this will have the most affect on lowering the
idle speed or rather changing it . Yet you said " If the idle changes
significantly, it means that less air is getting thru the AAR. The amount
of
idle speed change will give you an idea of how far the AAR is open." I'm
confused because I find the more air through the AAR there is is when I see
the idle change the most.

 I can see why the Idle air screw does not change the mix yet it is a path
around the closed throttle valve where the AAR is also a path around the
throttle valve , it's just a different path that slowly reduces as the
valve closes until it becomes no path , both past a closed throttle plate.
The idle air screw is fixed once it is adjusted for proper idle speed ,
once it is set then it still passes air and the same amount whether the AAR
is open or closed the AAR is simply additional air needed because of a cold
engine with a richer mix because of the TS2  needs more air to run and
because of cold thicker oil , it this what you are saying? .





On Tue, Oct 1, 2019 at 8:57 AM Jim Adney <jadney at vwtype3.org> wrote:

> On 30 Sep 2019 at 16:01, William Jahn wrote:
>
> > The only way to really know is pull the hose from the IAD to the AAR
> > and look before I start it. You can only see the slot from the IAD
> > side.
>
> You could do that, but that would be the hard way. The easy way would be
> to
> start the engine and remove the hose that goes from the air cleaner to the
> AAR. Leave the AAR end attached.
>
> Then block off the end of the hose with your thumb. If the idle changes
> significantly, it means that less air is getting thru the AAR. The amount
> of
> idle speed change will give you an idea of how far the AAR is open.j
>
> Just do this at the different stages of the warmup idle speed change, so
> you
> can tell what the AAR is doing at each point.
>
> > The entire point of the AAR is to be a vacuum leak to only richen
> > the mix by causing the MPS to keep the injectors to stay open a bit
> longer
> > along with TS2 and partly TS1.
>
> No, while this belief, or the opposite, gets repeated often, it's not
> true. If
> everything is working correctly, the MAP sensor compensates for the extra
> air and corrects the mixture. AAR open or closed, the mixture should be
> approximately the same richness.
>
> As you said, it's a vacuum leak, just like the idle adj screw, which also
> does
> not have any effect on the idle mixture.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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