o2 readings

[Walter Sherwin]

Thinking out loud here.....sounds like you have just recently added this O2
sensor to your conventional carb'd quadrajet setup, and that the O2 sensor
is not now (nor has it ever been) a part of a computerized feedback loop?
Also, with what are you measuring the small O2 sensor voltages, and what is
that device's input impedance?  Normally, a feedback O2 sensor (conventional
zirc) would be part of a larger signal conditioning circuit within a
computer, and would superimpose small voltages overtop a 450mv carrier
signal.  I'm not entirely sure what you would observe if you were to measure
the raw unconnected O2 sensor output voltages with say a normal DVOM.
Perhaps someone else has tried this and can relate to your numbers.

As for the wiring of your sensor, use your DVOM to check continuity from red
to black and then red to grey (you later called that one white).  Whichever
combo has the least resistance is your heater circuit pair.  The remaining
wire (probably the grey) will be your signal wire.  To measure the resultant
output voltages, you'll need to connect your test device from the signal
wire to the shell of the O2 sensor.  Your test device had better have at
least 10 Mohm input impedance, with closer to 100 Mohm being best (as per
Fluke's published data).

Walt.






> the o2 sensor is a Sorensen 779-7020, I bought it some time ago and just
had
> a bung welded in.
>
> I do not know if this is from a gm tpi application or not, I thought that
> they were all pretty much the same.
>
> does the wiring I have look right ? red=+12v, black = gnd, and white is
the
> sensor ?
>
> it varies between 11.09 at idle up to 36 mv with partial throttle. It
takes
> about 45 seconds or less for it to warm up and give me some readings.
>
> thanks, Diane
>
> thanks, Diane
> ----- Original Message -----
> From: "Programmer" <nwester at eidnet.org>
> To: <gmecm at diy-efi.org>
> Sent: Monday, January 01, 2001 3:30 PM
> Subject: Re: o2 readings
>
>
> > You're using a 3 wire heated ? Ok--happen to have the part number
> > handy ? With the numbers that low, the ECM is going to command
> > longer pulse on the mixture control solenoids--and go full rich.
> >
> > Lyndon.
> > -----Original Message-----
> > From: Diane Stowe <dianes at speakeasy.org>
> > To: gmecm at diy-efi.org <gmecm at diy-efi.org>
> > Date: December 31, 2000 2:14 PM
> > Subject: o2 readings
> >
> >
> > >Hello, a question. I thought I would test my newly installed 02 sensor
> > prior
> > >to my installing the new map tpi. I have a quadrajet on it now.
> > >
> > >I presumed that the red and black were 12v+ and -, and that the gray
lead
> > >was the sensor reading. The sensor is welding in a bung that is about
5-6
> > >inches below the passenger side exhaust manifold.
> > >
> > >anyway, with 12 to the o2 heater, which is on all the time, I get 11mv+
> at
> > >idle and somewhere between that and 36+ mv on driving up hills or
> > >strightaways.
> > >It never goes below that, or negative. Is this what I should be seeing
?
> my
> > >rpm never gets above 2300 due to the 700r4 and the 2:88 rear I have in
> the
> > >car. I am trying to track down the cause of the poor fuel mileage, it's
> > >about 10 mpg. that with a custom grind crower street cam, a new timing
> > >chain, a edelbrock performer and recently 21/2 inch pipes from the
> exhaust
> > >headers to the front mufflers and the installaiton of a crossover pipe
> > after
> > >the transmission. sadly none of these changes have helped much. I'm
> > assuming
> > >that the quadrajet is just running too rich, however I am not sure from
> > >these readings.
> > >
> > >thanks, Diane
> > >


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