Horace;

        The O2 sensor fine tunes the FI system to achieve stoichiometry.
A rich condition produces a voltage output from the sensor, about .9
volts. A lean detection results in no voltage. This cycle repeats itself
several times a second.
        My monitor has ten LEDs, each one represents 1/10th of the total
sensor output. This type of representation is called a moving dot
display. The sequential lighting of LEDs is analogous to an analog meter
movement.

Some O2 monitor observations from my truck:

1> When the engine is first started the Dot  "floats" in the middle of
it's range. This tells me the sensor is not grounded or otherwise
shorted.
2> As the engine/O2 sensor starts to warm the Dot creeps towards rich.
3> When the ECU switches to closed loop operation the Dot swings back and
forth rapidly.
4> At full throttle the Dot stays pegged in the rich zone.
5>When the idle position sensor is activated the system stays rich for a
few seconds then leans out for a few seconds.
6> An old O2 sensor caused the Dot to jitter and move lazily as opposed
to a new sensor which gave crisp and rapid Dot movement from one end to
the other.

 I am going to put together a batch of these soon. I am considering
adding a second similar gauge that monitors the charging system or
auxiliary battery (or all three). They should be relatively inexpensive.
Drive Safely & Good Luck
Ken Lewis<Kernersville,NC>86 VW crewcab;60 T-5 Coupe

On Sun, 28 Nov 1999 21:22:02 -0500 "Horace K. Sawyer"
<firestream@mindspring.com> writes:
>Your magic box sounds cool!  I might want one too, if it could be had.
>But, I do not understand the information that it shows us?  Why do we
>need
>to know this data?
>
>HK
>
>
>
>>        I am going to make another monitor for my wife's van. If you
>>would like one let me know. It is about the size of a match box and
>>should run around $20.
>
>

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