Date: Sun, 4 Feb 2001 03:27:47 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: O2 Sensor Voltage
In-Reply-To: <3A7C97EA.48088216@islandnet.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed
At 06:44 PM 2/3/2001, Mark Keller wrote:
>When looking at the activity of the "crossover" I believe that the basic
>fuel injection is out of adjustment and will cause an overactive
>crossover.
Not quite true...
> In other words if the fuel injection system is in proper
>adjustment, you should be able to disconnect the O2 sensor, and read the
>voltage from the O2 sensor black wire. Open loop voltage is very stable
True.
>and should be in the .5 volt range. Anything consistenly above .8 or
>below .3 volts needs to be corrected.
I'd be interested in expert opinion on this. The measurement range of the
lambda sensor is so tiny that it really only indicates "perfect," "too
rich," and "too lean" without giving any useful idea of how much. You can
get lambda sensors with an extended range, but they cost many hundreds of
dollars each, and wouldn't work properly with the ECU anyway. But if you
were rich you could add one as a monitoring device to read out on a meter
or LED bar graph.
>When the system is really tuned the O2 sensor will not crossover as
>rapidly as a system that is too rich,
This is wrong. The ECU treats the lambda sensor as having only two states,
too rich and too lean. Whichever way it finds, it kicks the mixture until
it goes the other way, then kicks it back, repeat forever. This goes on
many times a second at high rpm, and on an oscilloscope you could watch as
it happens. If you stick a regular digital voltmeter on it you'll simply
see a number that jumps around seemingly randomly, because the voltmeter
integrates over a noticeable chunk of a second to get a reading.
>.8 volt or higher, weak vane
>spring setting, malfunctioning fuel pressure regulator too high system
>pressure, Or too lean .3 volts malfunction of fuel pressure to low or a
>poorly adjusted afm wiper.
Voltage = oxygen present = too lean. IOW this is backwards. I still
question whether having an open-loop reading that's not in the middle of
the range is reason to begin fiddling in the absence of other indications
(smells rich, poor mileage, Rome burning... I dunno).
david
David Beierl - Providence, RI
http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
