[V8] O2 Sensor Readings

[cobram at juno.com]

Here's one that you can mount inside the car.   It fits with 3 wires
(+12v, signal wire on O2 sensor, and Ground).
 
http://tinyurl.com/39bfnd
 
MikeL's V8Q was going through O2 sensors, the temp sensor was the
culprit. 
 
He wrote to the u.washington list:
 
"It's easy to test.  let car sit overnight, then measure the resistance
between the 2 pins on the sensor.  Should be between 1.5 to 3 ohms.

Mine was at 4.5 and it made the car run so rich that you got a huge black
cloud when you stepped on it.  As well as a pile of soot under the
tailpipe
if you let it idle for 5 minutes.....

BTW,  This is what ruined my 02 sensor :-("
 
BCNU,
http://www.geocities.com/cobramsri/
We come into the world naked, screaming and covered in blood. Why should
the fun end there?
 
"d saad" <dsaad at icehouse.net> writes:
> 
> 
> I am not sure you can deduce much at all from this Scott.
> 
> The
> O2 sensor is not easy to read. To do it right, you really need an
> oscilloscope.
> A nice digital volt meter with a calibrated bar graph
> would also work OK - as long as the response time was fast enough. 
> The
> problem is that the sensor is a very high impedance device - so 
> just
> hooking up your meter affects the output. And the output is not a 
> steady
> state voltage - unless you are at extreme rich or lean condition. It 
> is a
> non-linear device with the usable range being a very narrow band 
> around a
> air/fuel mixture of 14.7. For most practical purposes, the sensor 
> can only
> tell you if you are above or below this number.
> If you look at the
> signal with a o-scope, you see something like a square wave - with 
> the
> duty cycle of the waveform indicating the mixture. A volt meter can 
> give
> you a rough idea of the duty cycle - because it averages the 
> readings, but
> it is a very rough indication.
> 
> 
> And - no - your O2 sensor
> wiring does not sound  OEM. Mine just snakes over the axle and 
> right
> into the connector. There are metal cable holders there to keep it 
> off the
> axle too.
> 
> Dave
> 
> > Can someone interpret these
> readings for me?
> > 
> > To induce a lean condition, I pulled
> the vacuum hose off the FPR*.  To
> > induce a rich condition, I
> plugged the FPR's vacuum hose and/or sprayed
> > some carb &
> choke cleaner into the hose (it was the only thing flammable
> > I
> had, besides electronic contact cleaner.. which I sprayed too).
> >
> 
> > First run, cold engine
> > Idle:  0.01 - 0.03 VDC
> > 1000 rpm:   0.02 - 0. 03 VDC
> > 2000 rpm:   0.23 - 0.28
> VDC
> > 3000 rpm:   0.29 - 0.35 VDC
> > 2500 Lean:  0.22 -
> 0.25 VDC*
> > 2500 Rich:   0.23 - 0.25 VDC
> > 
> >
> Second run, hot engine
> > Idle:  0.4 - 0.5 VDC
> > Idle Lean:
>  Very sluggish drop from 0.5 to 0.19* (sluggish meaning it
> > took
> 3-6 seconds)
> > 2500 rpm:  0.51 - 0.52
> > 2500 Lean:
> 0.52*
> > 2500 Rich: Sluggish rise to 0.66
> > 
> > * -
> in the end, the lean condition from the vacuum hose could have been
> > offset by the excess fuel dumped by the FPR
> > 
> >
> After the first run, I thought I'd nailed it.  A "lean" signal
> from the
> > sensor resulting in excess fuel being dumped which
> would explain my poor
> > mileage (8-10 city) and flutter/miss at
> idle on occasion.  But the
> > second run numbers look pretty good. 
> The lean condition at idle did go
> > down to the correct numbers,
> albeit sluggish.  The Lean 2500rpm can't be
> > trusted, IMO.
> > 
> > The only thing pointing to a bad sensor is the sluggish
> changes.  Should
> > I go ahead and replace the sensor or wait until
> my second-hand laptop
> > arrives for VAGCOM?  Sensor replacement
> was going to be a Ford but I
> > haven't decided on 3 or 4 wire.  Is
> 4 wire more trouble than its worth?
> > 
> > One last
> question:  How long is the sensor wiring?  Mine comes up from
> >
> the sensor, zip-tied to the transmission tube, then it loops to the
> > shock tower (zip-tied to the brake line brackets) before going
> back
> > under the distributor and plugging in.  Is this OE?
> > 
> > Thanks,
> > Scott S.