Date: Wed, 14 Feb 2007 11:53:45 -0800
Reply-To: Mike Frost <wasserleaker@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike Frost <wasserleaker@GMAIL.COM>
Subject: Re: The dreaded AFM adjustment screw
In-Reply-To: <e3d387a66f8f.45d33b4c@optonline.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Let me back up a bit here.
First, I am failing smog test for slightly high HC (300) and CO (1.45) so
that is the impetus for messing with things.
I have done the timing check and tried to adjust idle (with idle stabilizer
disconnected). I can't get the idle speed down to 920 without killing the
engine. The idle is stable when the idle stabilizer is connected, except for
occasional surges up to about 1100 RPM.
The other symptom happens once the engine is up to temperature, at which
point there is hesitation at the very beginning of the throttle (just past
the point where the throttle position switch disengages). This hesitation
can result in the engine dying at intersections. It seems to be worse after
sitting at idle for a while.
Other than that, there is plenty of power and reasonable gas mileage. I've
checked for vacuum leaks by spraying stater fluid everywhere.
I checked the voltage from the O2 sensor in open loop and it is hovering
around 0.84 or so. That is why I decided to adjust the AFM, it seems like
the mixture at idle is a bit rich. Not to mention the fact that the AFM has
been swapped and the 'new' one has never been adjusted since it was
installed.
If you think I am chasing the wrong demon, I am totally open to other ideas.
Mike Frost
86 Vanagon GL
On 2/14/07, dhaynes@optonline.net <dhaynes@optonline.net> wrote:
>
> The screw actually opens a bypass around the air vane. Clockwise closes
> the bypass making the mixture slightly richer. Counter clock wise opens it.
> If the O2 sensor is working properly the adjustment will not make a
> difference. The bypass is small enough that it only has an effect a idle.
> Why are you convincing yourself that you need to tamper with it? It it has
> been tampered with close and open two turns. Then fix what is wrong.
>
> Dennis
>
> ----- Original Message -----
> From: Mike Frost
> Date: Wednesday, February 14, 2007 10:55 am
> Subject: The dreaded AFM adjustment screw
> To: vanagon@GERRY.VANAGON.COM
>
> > So I have convinced myself that I need to adjust the mixture
> > screw on the
> > AFM but I have some trepidation about it. There are two things I
> > want to
> > verify before I begin:
> >
> > 1. To adjust properly, I disconnect the O2 sensor and measure
> > it's voltage
> > at idle, with a target of 0.5VDC.
> > 2. Turning the screw clockwise will lean the mixture?
> >
> > Mike Frost
> > 86 Vanagon GL
> >
>