Lamba sendor readings - advise needed

[Bruce Plecan]

-----Original Message-----
From: Quinton McCombs <quintonm at bellsouth.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Wednesday, September 16, 1998 9:59 PM
Subject: Lamba sendor readings - advise needed


Disclaimer:
I have not worked on a closed loop rotary, and the following is
just a few things that I've noticed found on normal ICE engines
and O2s
>
>First when the car is at idle (about 1K RPM), the O2 sensor >normally reads
around .85v.  As I continue to idle the voltage will >drop at ablout a rate
of .01 volts per 5 seconds.  I am assuming >that the exhast temp is just
cooling down.  I have not monitored it >long enough to see what it settles
down to.  After about 5 minutes it >wil settle around .65v.  Is this a
correct assumption?

As the O2 sensor cools it becomes more sensitive to other gases,
than O2 (Please refer to the archives about CARB, EPA, and
exhaust gases, for complete details).  Also, the meter is AVERAGING the
pulses.  Your probably on a DCv scale, and the
O2 is almost like the top of a sine wave (Someone with a EED
can probably better explain how that looks).
>
>Next, I seems to been running lean intermittantly.  I finally figured out
>that any electrical load on the car (head lights, brakes, fan, power
>windows, etc) will cause the O2 reading to drop by .02v - .03v >almost
instantly.  Now I am not sure it the O2 readings are accurate >at all.  Any
idea what could be causing this?


Any load changes the metering, and timing.  .02v is a very small
O2v change.
>
>Finally, I have noticed a strange problem which appears under full load at
>>6k RPM.  The car acts like it hits fuel cut for about 1 - 1.5 seconds.  I
>noticed that when this happened by O2 reading dropped from around .83v to
>.65v.  Just after the car picked back up, the O2 reading went back to .85v.

Could be also a 100 mechanical items.  Not gonna try and guess
engine diagnosis.

> When this occurred I was running approx 10PSI @ 6500 RPM 3rd gear.  I have
>a PFC FCON with a fuel cut defensor.  Other mods as well, but these are the
>only ones that I could see affecting the fuel delivery.  Ideas?
>
>Also, what are acceptable readings from the O2 sensor under full trottle,
>crusing, idle, and deceleration?  Under full throttle I will run anywhere
>from .91v to .83v.  Level ground maintaining speed voltage is anywhere
>between .30v and .65v. Very slight acceleration .80v - .85v and just
>slightly more will drop it to .75v - .80v.  Idle is around .82v - .85v (for
>a little while).  Deceleration will drop to very small negative voltage (I
want to say around -.025v range).

Those numbers don't sound very strange or unusual.
Cheers
Bruce
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