Date: Sat, 27 Jun 1998 17:20:50 -0500
Reply-To: Darrell Boehler <midwesty@TAOS.MIDWEST.NET>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Darrell Boehler <midwesty@TAOS.MIDWEST.NET>
Subject: Re: new O2 installed - engine dies
Content-Type: text/plain; charset="iso-8859-1"
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Hi Michael ,
Let me explain by giving you some meter readings from my 86 digifant /
oxygen sensor and maybe you can discern where your problem is. All readings
will be from frame or ground.
Lets start by disconnecting the oxygen sensor , with the key on, the
wire from the oxygen sensor connector to the digifant pin 2 reads 0.5 volts.
With the engine running this wire will still read 0.5 volts . You can drive
around all day and it will read 0.5 volts. This is the norm.
Now lets meter the wire from the oxygen sensor. Still with oxygen sensor
wire disconnected from the wire that goes to the digifant. With the key on
the voltage will be 0.0 volts until we start the engine. Once the exhaust
starts to warm the oxygen sensor, aided by the internal oxygen sensor
heater, the oxygen sensor will start to produce a voltage output. The
amount of that voltage will depend on how rich your mixture your digifant
producing for your engine in default mode. Note we will be in default mode
until the oxygen sensor produces a voltage to the digifant for about 30
seconds. Since we are disconnected the digifant will not see a voltage from
the oxygen sensor and will stay in default mode. My oxygen sensor voltage
runs at 0.0 volts for 0.5 to 1 minute , depending how hot the sensor is
before starting the engine. If it were very cold it would take longer than 1
minute. After 1 minute the voltage climbs to to 0.9 volts and stays there.
The oxygen sensor is getting a pretty rich reading in default mode, my van
seems to run ok in this mode but mileage would not as good as normal.
With the van still running if I plug the oxygen sensor connector back
together the voltage reading will stay at the 0.9 volt level for 30 seconds
. Then the digifant has discerned the oxygen sensor is working and has is
detecting a rich mixture and by 35 seconds my digifant has the oxygen
sensor voltage readings bouncing above and below the 0.5 volt range. 0.5
volts reading indicates a perfect mixture. The bouncing of the oxygen
sensor voltage above and below 0.5 volts is the way all ECU's seem to
operate.
With it connected if I observe my oxygen sensor voltage starting from a
warm stopped engine. My reading is 0.0 volts for about 30 sec. 0.9 for
exactly another 30 seconds and then I get the rapid fluctuations as the
digifant takes the con.
Your reading in default mode may be less than the 0.9 volts I read but
it should be above the 0.5 volt area. Hope this helps and good luck with
your van.
Darrell Boehler
Makanda Illinois
-----Original Message-----
From: Michael Sullivan <sullivan@OPENMARKET.COM>
To: Vanagon@VANAGON.COM <Vanagon@VANAGON.COM>
Date: Saturday, June 27, 1998 2:40 PM
Subject: new O2 installed - engine dies
>Dear List,
>
>I finally got around to installing a new 3-wire O2 sensor (generic from Ron
@ Bus Depot) on my 87 Westy Syncro. Splicing was done properly (soldered w/
heat shrink). Car started normally. Once warmed up however, engine lost all
power, couldn't even keep an idle. Short story: I had to disconnect my new
O2 sensor to get back home.
>
>So, this makes me think that the old one was, in fact, bad and that the
PO's mechanic simply adjusted the car to run "ok" with a bad O2 sensor. Am I
right? (note: gas mileage wasn't all that great before -- 15mpg -- and
horsepower was adequate but not as good as another Vanagon owner's car which
I have driven).
>
>Or is it possible that the new O2 sensor could be bad?
>
>I tried getting a reading from my DMM but I couldn't get a steady reading
at idle. Another thing: engine now (with no O2 sensor) idles steady - no
1-second fluctuation between 900 and 950rpm. Also, if I pull off the vacuum
hose to the fuel pressure regulator, nothing happens, even leaving the hose
sucking air into the engine. Does that mean my engine is now running ruch?
>
>I noticed quite a few threads on this subject in the archives, but I could
not find a lot of actual answers/solutions. Any help would be greatly
appreciated.
>
>Cheers,
>
>
>Michael J. Sullivan
>Director of Catalog Design
>Open Market, Inc.
>
>'87 GL Syncro Westfalia
>********************************************
>work: http://www.openmarket.com
>vanagon: http://www.hsdesign.com/vanagon
>scan tips: http://www.hsdesign.com/scanning
>********************************************
>
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