RE: Oxygen sensor question

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

I'm not an OXS expert, but I do know a bit about how it is supposed to work
...

I guess my first question would be to ask how you are actually measuring the
voltage ... the OXS is a high impedance source and if you are using a meter
that doesn't have a high input impedance it may affect your reading ...
otherwise the range you describe sounds within the proper range for an OXS
... assuming that the measurements are valid it seems to me that a wildly
fluctuating reading could mean one (or more) of 3 things ...

1) As you suspect ... the OXS is bad ... 
2) The other end of the control loop is not working ... this would mean that
the ECU is not running in a closed loop mode for some reason (bad temp
sender?), or the OXS frequency valve/differential pressure regulator (I
don't recall what kind of car you're working on) isn't regulating things as
it should.  
3) You've got one or more cylinders misfiring or running with a different
mixture than the rest, which is causing the OXS' output to fluctuate.  Since
the feedback loop has only one control variable and it applies to all
cylinders it can't make all cylinders have the correct mixture ...

I don't know which of the possibilities is the one most likely to be at
fault, but I would try looking into the other possible sources before
swapping the OXS ... it seems to me that I recall you posting info about
your problem, but I'm sorry to say that I don't recall what you've done to
date, but misfiring could be due to bad
coil/driver/wires/cap/plugs/distributor or a mixture problem could be due to
leaky injectors or something similar.  

I think I'll post this so that others with more experience can comment on my
theories ... good luck Mark!

Steve Buchholz
San Jose, CA (USA)

> ----------
> 
> Does anyone know what the output from the o2 sensor should be.  I know it
> should generate a .5 volt signal at lambda, but the reading I am getting
> from mine fluctuates from about .2 volts to 1 volt.  It just swings back
> and
> forth erradacly.  Is this normal or should it be more of a steady reading?
> Do you think that it is the engine causing the fluctuation a bad o2
> sensor?
> 
> Thanks for any help
> 
> mark@afnetinc.com
> 
>