weird o2 sensor readings? (mc'd urq)

Huw Powell audi at
Mon Jul 7 02:56:45 EDT 2003

> ok... i figured, though, that it wouldnt be jumping from 0-1 volt
> constantly, but within a smaller range...  otherwise those a/f gauges
> would be going from blank to fully lit constantly...
> iwas under the impression that the voltage signal would start to
> stabilize a bit under load, hence the desire to have a .9-.95 volt
> reading...

absolutely not, this is a feedback loop that is constantly correcting
itself by over-running *very slightly* in each direction.

>> and finally, when i turned off the car, the voltage reading
>>>  stayed there, and was around .550v

that is just a voltage that appears on the ECU.

> i understand it fluctuates, but i was also under the impression that
> the fluctuation was within a sub-range of the 0-1 volt reading, which
> is where stoich is

anywhere between .2 and .8 or so volts on an OXS *is* stoich.  They are
a very fine tuned device.  slightly rich or slightly lean, meaningfully,
that is, is off-scale.

> trust me, i tried that.  i set it to be 'exactly' within specs of the
> bently at 50%  dc +-8%.  it had no power above 3k rpm. then i
> listened to listers advice that i had in the archive and set it at
> 35-40% for a richer mixture.

Richer at WOT and cold - still close to stoich in closed loop.

>  that helped a little, but not very
> much.  then i tried 20%, again, helped more, but not very much.  now
> it is somewhere around 4% pegged, because the frequency valve doesnt
> even turn on at idle it is so rich, and FINALLY im gettinga little
> bit of power...
> so there's something going on in there that i havent found yet...

Yes, something else is really broken.  I would follow the listers advice
who suggested a "new" (used) fuel distributor - try to swap in some
other parts to see what effect they have.  Do you have access to a field
full of junked cars that ran when they died?

Huw Powell

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