<div dir="ltr"><div><br></div><div> 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.</div><div><br></div><div> 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? <br></div><div><br></div><div> 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 <br>
significantly, it means that less air is getting thru the AAR. The amount of <br>
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. <br></div><div><br></div><div> 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? . <br></div><div><br></div><div> <br>
</div><div><br></div><div> <br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Oct 1, 2019 at 8:57 AM Jim Adney <<a href="mailto:jadney@vwtype3.org">jadney@vwtype3.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 30 Sep 2019 at 16:01, William Jahn wrote:<br>
<br>
> The only way to really know is pull the hose from the IAD to the AAR<br>
> and look before I start it. You can only see the slot from the IAD<br>
> side. <br>
<br>
You could do that, but that would be the hard way. The easy way would be to <br>
start the engine and remove the hose that goes from the air cleaner to the <br>
AAR. Leave the AAR end attached.<br>
<br>
Then block off the end of the hose with your thumb. If the idle changes <br>
significantly, it means that less air is getting thru the AAR. The amount of <br>
idle speed change will give you an idea of how far the AAR is open.j<br>
<br>
Just do this at the different stages of the warmup idle speed change, so you <br>
can tell what the AAR is doing at each point.<br>
<br>
> The entire point of the AAR is to be a vacuum leak to only richen<br>
> the mix by causing the MPS to keep the injectors to stay open a bit longer<br>
> along with TS2 and partly TS1.<br>
<br>
No, while this belief, or the opposite, gets repeated often, it's not true. If <br>
everything is working correctly, the MAP sensor compensates for the extra <br>
air and corrects the mixture. AAR open or closed, the mixture should be <br>
approximately the same richness.<br>
<br>
As you said, it's a vacuum leak, just like the idle adj screw, which also does <br>
not have any effect on the idle mixture.<br>
<br>
-- <br>
*******************************<br>
Jim Adney, <a href="mailto:jadney@vwtype3.org" target="_blank">jadney@vwtype3.org</a><br>
Madison, Wisconsin, USA<br>
*******************************<br>
<br>
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