weird o2 sensor readings? (mc'd urq)

[Jesse Clendenning]

When you receive the fuel pressure gauge, I'm guessing you find that the
warm-up regulator is causing your mixture to go lean.

This happened to me. I could not figure out what is was until I received an
O2 meter. I could set the idle fine. I set out on my maiden voyage with me
newly installed meter and found under very light throttle I could get around
and the mixture would be OK. The moment I gave it little acceleration or
more, the meter would instantly go off the gauge lean.

I replaced my warm-up regulator when I received my fuel pressure gauge. I'm
learning what a 10v turbo can really do.

Jesse Clendenning

----- Original Message -----
From: "Michael S. Williams" <mike at borderlinemotorsports.com>
To: "Nate Stuart" <newt at newtsplace.com>
Cc: <quattro at audifans.com>; <urq at audifans.com>
Sent: Monday, July 07, 2003 12:11 AM
Subject: Re: weird o2 sensor readings? (mc'd urq)


> At 9:57 PM -0400 7/6/03, Nate Stuart wrote:
> >  > so, here's where the weirdness started... the display was showing
> >>  about .400-.600v at idle, and would drop quickly under load, to
> >>  almost zero....  so, i pulled over and turned the mixture screw about
> >>  1/2 turn clockwise (i know that's alot)... enough to cause the
> >>  frequency valve to shut off at idle... got back in the car, and at
> >>  idle, itwas reading about .800-.900v... ok... SEEMS closer... but
> >>  assoon as i got on the gas, it would drop...
> >
> >You cannot use a multimeter to tune a closed loop O2 system. The O2
sensor
> >voltage does not stay at a steady point, instead it fluctuates back and
> >forth very quickly from lean to rich readings, as the ECU adjusts the
> >mixture. I have yet to see a multimeter that refreshes/samples fast
enough
> >to even come close to properly displaying an O2 sensor output, especially
> >under load/high RPM, where the cycle rate is very fast. Do not tune the
> >engine based on the multimeter readings. You're not going to be able to
> >ever get the 'correct' O2 reading this way, as the ECU will continually
be
> >adjusting the mixture anyway.
>
> 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...
>
> >  > but here's the strange thing.  the car had a LOT more power, and the
> >>  reading dropped BELOW 0v, into 'negative' voltage, about -.02 or
> >>  so....  and finally, when i turned off the car, the voltage reading
> >>  stayed there, and was around .550v
> >
> >Yup, things like that will happen, it's usually because the meter is not
> >capable of measuring the fluctuating signal correctly.
>
>
> ok
>
> >
> >>  but, like i said, the power is closer to where it is supposed to be,
> >>  it isnt using coolant, the compression is almost exactly the same
> >>  across all 5 cylinders, the o2 sensor is brand new, the idle/wot
> >>  switch is new, the temp sender for the isv is new, the michelin man
> >>  hose is new, i checked and rechecked the intake hosing, inspected the
> >>  vacuum lines.....nothing....
> >
> >It may have been that you were running lean before, for some reason, so
> >your adjustments may have helped, but they are probably not where they
> >should be. Wait until you get that real A/F ratio gauge. At the very
least
> >that will have a fast enough display to show you roughly where your
> >mixture lies.
>
> 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, and that's where the a/f ratio gauges indicate
> green/blue/whatever
>
> >Also, double check the Bentley for the proper baseline
> >setting of the CIS system, it's really a lot simpler than you are making
> >it out to be.
>
> >  If I recall correctly you just need to measure the OXS
> >valve's duty cycle at warm idle, and turn the mixture screw until the
duty
> >cycle falls within a specified range. It's been a while since I've ever
> >mucked with this (yay for programmable efi ;), so I may be way off of the
> >procedure, but it is in the Bentley. If you need I can dig it up
sometime.
>
>
> 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.  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...
> that's why it seems im making it more complex...
>
>
> >
> >>  the one thing i dont have on hand is a fuel pressure gauge, but im
> >  > gonna order one, since it seems like it's a good idea to have anyway,
> >>  esp w/ the cis....
> >>
> >>  anyone have any thoughts?
> >
> >Yeah, that definitely doesn't hurt to have with a CIS car, as everything
> >is based off of the system pressure.
> >
>
> yup...
>
> thanks for the advice...
>
> and i have read about the benefits of the efi, trust me, it's on my
> mind right now...heh...
> --
> MswmSwmsW
>
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