Hi Jay,

The 02 goes to nothing when you let off the gas may be the closed throttle
switch shutting off the fuel. Mine goes to zero also.

I opened my AFM and adjusted the spring one way then the other. Then I drove
it to see how it ran. I am currently at 10 notches less spring tension than
stock. This is not quite right but it runs well.

At 3K in open loop I'm at .8 volt also. I tried to increase tension on the
spring to get around .7 volt at 3K in open loop, but the van lost all power
just of idle. I was at a intersection and didn't have the power to get out
of the way! So a person needs to try out their changes on a safe street.

The voltage in closed loop is supposed to bounce back and forth of .5 volts
at idle and when cruising. Mine does that.

I constantly monitor my 02 while driving with a digitool.

Happy Travels,
Mark Ingalls

I constantly monitor my 02 voltage

>From: Jay L Snyder <Jay.L.Snyder@USA.DUPONT.COM>
>Reply-To: Jay L Snyder <Jay.L.Snyder@USA.DUPONT.COM>
>To: vanagon@GERRY.VANAGON.COM
>Subject: Tuning by O2 Sensor
>Date: Mon, 19 Mar 2001 10:23:32 -0500
>
>I decided to run my '85 1.9l with the O2 sensor unhooked from the FI system
>and wired to my digital voltmeter.  The readings were high, consistently
>ranging from 0.8 to 0.85 VDC.  I then reconnected the O2 sensor and then
>"teed" in the voltmeter.    The ECU adjusted the mixture some, dropping the
>voltage to 0.7 to 0.75 VDC.  Is this still too high?  Is it worth opening
>up the AFC and tinkering with the spring?
>A couple of interesting observations.  The O2 sensor puts out a usable
>voltage in less than a minute---this is the one-wire type.  I thought it
>would take several minutes to heat up.  When you get off the gas, the O2
>sensor voltage drops to almost nothing, and then recovers after a steady
>exhaust flow is established.  It takes awhile at idle to level out.  The
>WOT switch does work!  It goes to 0.9VDC when you floor it--with or without
>the O2 sensor connected.
>My conclusion is that if your engine runs better with the O2 sensor
>disconnected, you have other problems. You probably have a  vacuum leak and
>the richer open loop mixture helps correct it.
>How many notches should I move the AFC spring (and which way) to lean it
>out?  This a new AFC, by the way.
>As a side note, I am running my timing at  "0" TDC and it does seem to run
>better.  I am hesitant to advance it much farther.  Would this affect the
>O2 sensor readings?
>                                                    Jay '85 Westy

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