Date:         Sat, 17 Aug 2002 09:55:22 -0400
Reply-To:     "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Organization: Bulley-Hewlett
Subject:      O2 Sensorama, was: A few unrelated questions
In-Reply-To:  <B983C505.1E01%danoer1@eclipse.net>
Content-Type: text/plain; charset="US-ASCII"

O2 sensor not important, eh? Just for 'clean air wack-o's' eh?

From a functionality/engineering perspective, the O2 sensor is eyeballs
of the fuel injection system. Without it, the ECU is practically blind.

Think of it this way, your FI system has three basic components;
sensors, injectors, and a brain to guide the quantity of fuel injected.
In the category of "sensors" you have some that pick up semi-extraneous
data on temperature around the motor, air flow coming in, etc. which it
crunches into a firing solution for the injectors.

The "final analysis" or QC for the fuel system is the O2 sensor. It sits
in the exhaust stream and measures EXACTLY how the combustion process is
working.

The O2 sensor is the ONLY sensor in the FI system that actually measures
how well the system is achieving its goal of delivering maximum HP and
efficiency with each cylinder firing. The rest of the sensors are all
"preliminary" data that proceeds the firing cycle. Does this make sense?
The O2 sensor is like a QC guy at the end of a factory assembly line
with a hotline to all of the production stations in the factory, and
authority to tell each of those stations what to do to improve the
product coming out of the factory.

It is so vital to the operation of your engine, that VW put a warning
light on the dash that reminds you to replace it every 30k. VW is not a
warning-light-happy company. Failing to replace The 02 sensor eventually
leads to the van reverting to the very lame "limp home" program in the
EFI ECU. This limp home program has been known to ruin/melt catalytic
converters because it tends to run very rich. It also fouls plugs, and
yields poor mileage, and poor performance.

So, if you haven't splurged for the amassively expensive ($30) O2
sensor, stop being a cheapskate. Go get the sensor.


Developing business and guiding change since 1996,

G. Matthew Bulley
Bulley-Hewlett
Marketing & Communications
Business: www.bulley-hewlett.com
AIM = IExplain4u
Phone: +1.919.658.1278


-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
Of Dan Erlandson
Sent: Saturday, August 17, 2002 9:18 AM
To: vanagon@GERRY.VANAGON.COM
Subject: A few unrelated questions

Hey everyone,

Just joined the list... great info.

My 91 GL has 167 K on it with a rebuilt engine and rebuilt auto tranny.
It
is running fine these days, but a couple of questions

1.  I seem to read in the postings that the O2 sensor has some impact on
the
smoothness of the running of the engine.  I guess I thought it was just
an
emissions issue.  If it has never been replaced then I should replace
it?

2.  The fresh air fan, a.k.a. defroster/heater  fan for the front seems
to
have gone bad.  Smoke and bad fumes when you turn it on.  No problem as
long
as it isn't on.  Bentley indicates that you have to pull the whole
dashboard
in order to access the fan.  I ordered one from VW and am close to
starting
the procedure.  Any advice?  Also picked up a couple of the shear bolts
that
hold the steering column to the dash (as per Bentley).


-- Dan Erlandson
Flemington, NJ
> danoer1@eclipse.net