Date:         Mon, 19 Mar 2001 14:49:15 -0700
Reply-To:     Steve Blackham <steph@USWEST.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Steve Blackham <steph@USWEST.NET>
Subject:      Re: Tuning by O2 Sensor
Content-Type: text/plain; charset="us-ascii" ; format="flowed"

Vacumn leaks will make it run lean.  Exhaust leaks will make it run
rich (O2 connected).  I suspect that most of these problems are
exhaust leak related.  Warm your engine up.  Put a hand and rag on
the tail pipe.  Listen for where and if any exhaust is leaking
elsewhere.  Minute exhaust leaks can cause an O2 sensor to go nuts.


Check all the exhaust pipe connection gaskets, especially the
Y-joint.  Spray a little soapy water on them.  I bet you'll find your
problem.  Check the seal on the O2 sensor.


Thanks

Steve


Jay L Snyder <Jay.L.Snyder@USA.DUPONT.COM> wrote:

Date:    Mon, 19 Mar 2001 10:23:32 -0500
From:    Jay L Snyder <Jay.L.Snyder@USA.DUPONT.COM>
Subject: Tuning by O2 Sensor

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

--
Steve Blackham
Centerville, Utah

77 transporter converted to camper (Westy top)
83 Vanagon  (New and current project)
87 Weekender