[V8] O2 Sensor Readings
cobram at juno.com
cobram at juno.com
Tue Jul 3 23:13:50 EDT 2007
Here's one that you can mount inside the car. It fits with 3 wires
(+12v, signal wire on O2 sensor, and Ground).
MikeL's V8Q was going through O2 sensors, the temp sensor was the
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
if you let it idle for 5 minutes.....
BTW, This is what ruined my 02 sensor :-("
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.
> O2 sensor is not easy to read. To do it right, you really need an
> A nice digital volt meter with a calibrated bar graph
> would also work OK - as long as the response time was fast enough.
> problem is that the sensor is a very high impedance device - so
> hooking up your meter affects the output. And the output is not a
> 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
> duty cycle of the waveform indicating the mixture. A volt meter can
> 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
> into the connector. There are metal cable holders there to keep it
> off the
> axle too.
> > 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
> > 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:
> > 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
> > under the distributor and plugging in. Is this OE?
> > Thanks,
> > Scott S.
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