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
>