Date: Sun, 8 Jul 2012 08:57:32 -0400
Reply-To: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject: Re: At Idle: AFM Flap, CO Screw Relationship. Explanation Found
In-Reply-To: <CAB2RwfhfLbH7jqVSE8qHWjSZOJZt0eKNDy=gnOMf4fjvR9S0aA@mail.gmail.com>
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With the sensor disconnected from the engine the mixture screw should affect
the O2 sensor reading. You want to adjust for about .5 volt. This is usually
as little as 1-2 turns open. Even fully closed the O2 sensor should
compensate. On the 1.9L engines incorrect setting can add to the factors
that cause that idle surging.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
neil n
Sent: Sunday, July 08, 2012 2:59 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: At Idle: AFM Flap, CO Screw Relationship. Explanation Found
Thanks Dennis.
Out of curiosity I shaped, and duct taped a toilet roll (such Kustom
Werk) to approximately fit in outlet of air bypass. Blowing into the outlet,
I opened and closed the CO screw. Though this was a buck-shee method, it
really seemed to me that with screw in all the way, the air bypass was
closed.
As per your other post, I measured the voltage output of the O2 sensor
(after disconnecting, engine off) while turning the CO screw. I saw higher
voltages ( ~ 0.8 ) and the output fluctuated some (maybe analogue VOM better
for this purpose?) but in general, adjusting the CO screw affected the O2
voltage output. Maybe the sensor had cooled down prior to test (had engine
up to temp, then it sat for about 10
minutes)
Will recheck timing then test O2 voltage output again, right after engine up
to temp.
Not sure why a PO set the CO screw all the way in (bypass closed off).
Compensate for a vacuum leak? Worn throttle body valve? I have yet to make a
smoke tester but have re-tested the air intake bellows and its'
2 pipes for leaks (none) and repaired a small leak at ISV 3 way boot.
(yes. Permatex silicone and small shaped piece of fuel hose can repair a
leak at the small pipe)
btw. Here's a neat explanation, "how to" and video made by Chris Corkin (aka
Tencent) on measuring the AFM. Really cool and useful.
http://www.thesamba.com/vw/forum/viewtopic.php?t=369815&highlight=afm+test
video link here:
http://s105.photobucket.com/albums/m218/tencentlife/van%20tech%20items/?acti
on=view¤t=MOV02923-1.mp4
Neil.
On Sat, Jul 7, 2012 at 11:19 PM, Dennis Haynes <d23haynes57@hotmail.com>
wrote:
> The air bypass or mixture adjusting screw will not bypass enough air
> for the AFM vane to stay closed. If it could than the air cooled
> engines would have a problem as the AFM vane has to open to run the
> fuel pump. It is just a trim adjustment. It must be noted that when
> trying to adjust this you need to disconnect the O2 sensor and restart
> the engine after the disconnect to not have any O2 sensor
> compensation. Adjust fir ~.5 volt at the sensor with it disconnected.
> Then when you connect it you should see the system react and change the
sensor readings. Normal fluctuation should be ~.2 to .8 volt.
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> Behalf Of neil n
> Sent: Friday, July 06, 2012 4:52 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: At Idle: AFM Flap, CO Screw Relationship. Explanation Found
> http://www.race.nangreaves.com/golf/FU01/ch7.6.html
> .... I had figured that the air bypass, at idle, would allow the AFM
> to stay closed. e.g. that air bypassed this flap and that the mixture
> was controlled by adjustment of air only, via the CO screw. Not true it
seems.
--
Neil n
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