Date: Thu, 2 Nov 2000 19:02:17 EST
Reply-To: kenneth d lewis <kdlewis@JUNO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: kenneth d lewis <kdlewis@JUNO.COM>
Subject: Re: O2 Sensor, Bucking etc.
Gary;
Was an electric stove? Possibly voltage induced by magnetic
fields from the coils. The following is one of my past dissertations
about O2 sensors.
Drive Safely & Good Luck
Ken Lewis <Kernersville,NC>
86 VW crewcab;60 356B Coupe
--------------------------------------------------
Diagnosing Oxygen Sensors:
The oxygen sensor is really a simple device : It tells the engine
computer how much O2 (oxygen) is left in the exhaust . With this
information the computer can determine the best air/fuel ratio ;
stoichiometry.
When the O2 sensor detects too little oxygen in the exhaust it tells the
computer the engine is running rich (please send less fuel).On the other
hand too much O2 means a lean mixture (please send more fuel).
The O2 sensor kind of acts like a fuel cell(a battery is a good analogy).
A voltage is produced (1 to 1.5 volts) when there is a difference of
oxygen levels between the inside of the sensor(the environment air) and
the outside of the sensor sitting in the exhaust stream . This indicates
a rich condition or to little O2.When there is O2 in the exhaust (lean),
the inside and outside of the sensor has less O2 differences and the
voltage output drops to zero.
BUT the sensor must reach operating temperature to work(real hot) i.e.
the computer ignores any input from sensors on a cold engine. This is
known as "open loop operation",the computer wings it.After the sensor
heats up the computer goes into "closed loop operation".The sensor
detects a lean mixture then the computer allows more fuel from the
injectors. This produces a rich mixture,sensor voltage drops,computer
leans out the mixture.An endless cycle. In other words the mixture never
stabalizes at perfect but continuously toggles around it.
If you have a good voltmeter you should see this voltage swing from a
fully heated operational sensor.
You can test your system with a 1.5 volt flashlight battery. Disconnect
the sensor lead. This is easiest deduce with a single wire sensor. Three
wire sensors have two wires for a heater, DONT mess with these.Connect
the negative side of the battery to chassis ground. touch the sensor wire
going to the computer to the positive side of the battery.This fools the
computer in thinking there is a rich mixture present. It attempts to
correct by leaning out the mixture ,hopefully making the RPM's drop.The
output of the sensor should drop also.
On the other hand if you ground the sensor lead going to the computer it
thinks the there is a lean mixture and attempts to compensate by send
more fuel hence the engine SHOULD surge. At this time the output of the
sensor should climb.
On Thu, 2 Nov 2000 07:50:30 -0500 Gary Stearns <gstearns@SPRINTMAIL.COM>
writes:
>This is a multi-part message in MIME format.
>
>------=_NextPart_000_002A_01C044A1.92947480
>Content-Type: text/plain;
> charset="iso-8859-1"
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>Here's one for you. Last night I removed our O2 sensor and did a
>little =
>test. I brought it inside, connected it to a digital mult-meter and =
>heated it (gently) over an electric stove. At first the meter read
>0.00, =
> within about 15 seconds it started bouncing around between 0.17 and =
>-0.17. I realize that without an exhaust stream these values are =
>irrelevant. What was amazing was that I got these readings without
>the =
>black lead on the meter connected to anything. The signal wire on the
>=
>O2 sensor was connected to the red lead. The wire is not coaxial so =
>there is no ground confusion here. When I touched the black lead of
>the =
>meter to the O2 body or threads it made no difference in readings. I =
>consistently read an output from the sensor with the black lead of the
>=
>meter hanging in mid air! Are these sensors magic or was my stupid
>test =
>creating static voltage or a "force field" or something? Try it!
>
>Gary
>
>------=_NextPart_000_002A_01C044A1.92947480
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> charset="iso-8859-1"
>Content-Transfer-Encoding: quoted-printable
>
><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
><HTML><HEAD>
><META content=3D"text/html; charset=3Diso-8859-1" =
>http-equiv=3DContent-Type>
><META content=3D"MSHTML 5.00.2614.3401" name=3DGENERATOR>
><STYLE></STYLE>
></HEAD>
><BODY bgColor=3D#ffffff>
><DIV><FONT size=3D2>Here's one for you. Last night I removed our O2 =
>sensor and did=20
>a little test. I brought it inside, connected it to a digital =
>mult-meter=20
>and heated it (gently) over an electric stove. At first the meter
>read=20
>0.00, within about 15 seconds it started bouncing around between
>=
>0.17 and=20
>-0.17. I realize that without an exhaust stream these values
>are=20
>irrelevant. What was amazing was that I got these readings
>without =
>the=20
>black lead on the meter connected to anything. The signal wire
>on =
>the O2=20
>sensor was connected to the red lead. The wire is not coaxial so there
>=
>is no=20
>ground confusion here. When I touched the black lead of the
>meter =
>to the=20
>O2 body or threads it made no difference in readings. I =
>consistently read=20
>an output from the sensor with the black lead of the meter hanging in
>=
>mid=20
>air! Are these sensors magic or was my stupid test creating
>static =
>voltage=20
>or a "force field" or something? Try it!</FONT></DIV>
><DIV> </DIV>
><DIV><FONT size=3D2>Gary</FONT></DIV></BODY></HTML>
>
>------=_NextPart_000_002A_01C044A1.92947480--
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