[T3] '72 FI won't idle down

[Keith Park]

Well it does run lean when warm with the AAR Open, used to see it when I had
the AFR meter on it and it tends to miss then too, we'll see what happens
when I close that off when the engine is hot.

Keith


Topnotch Restorations
topnotch at nycap.rr.com
http://www.topnotchresto.com
71 Squareback  “Hothe”
65 Notchback  “El Baja Rojo”
93 RX7  “Redstur”
13 Subaru Outback "Blendin"

-----Original Message-----
From: type3-vwtype3.org <type3-vwtype3.org-bounces at lists.vwtype3.org> On
Behalf Of Jim Adney
Sent: Saturday, June 13, 2026 1:20 AM
To: type3 at vwtype3.org
Subject: Re: [T3] '72 FI won't idle down

On 12 Jun 2026 at 21:13, Keith Park wrote:

> Well, if your at, say, 1/8 throttle accelerating, your going to run 
> leaner with the idle air bypass than you are without it right?  
> Remember, this is a T4, may be a bit different...

That reasoning only works if the fresh air can slip in without the pressure
sensor noticing. That would be the same as saying we should never press down
on the throttle, because that will lean out the mixture.

No matter the route, any air getting into the IAD is the same as any other
air, and the pressure sensor measures the total pressure, where the total
pressure is the sum of all the partial pressures from each source. The
pressure sensor can't tell and doesn't care where each molecule came from.

--
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************

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