Eractic O2 sensor

[Ken Kelly]

Andy,
	Your readings are correct and accurate. The standard O2 sensor really behaves
more like a switch than a linear scale. Your PCM/ECM just looks for it to switch
accross the 14.7 to 1 voltage. As soon as it crosses the ECM starts to force it
the other way while it is in closed loop. That means that in closed loop (read
part throttle) it will oscilate back and forth at a fast rate. At Wide Open
Throttle it goes into Open loop, and tries to set the AFR to about 12 to 1
therefore the ocsillation stops.

	You really need a wide band O2 sensor to get good readings. Some people claim
that with adequate damping you can get a sense of the AFR from a standard O2
sensor. You obviously don't have enough damping in your circuit.

		Ken

Andy Lawrence wrote:
> 
> Hello
> 
>     I have built Dave Morrill's O2 sensor on the efi332 web site, hooked it up
> to my chevy truck.  At all throttle positions except full throttle the reading
> on the O2 sensor meter is extremelly eractic.  It moves from 1 to 5 faster
> than i can see it! But while at full throttle the reading is consistant at 5!
> Why would it be so eractic off of full throttle?
> 
> I know that the O2 sensor is working properly because i hooked it up to a
> variable supply and ran though the 0 to 1 volt range watch the light count by
> the .10 of a volt....
> 
> The O2 sensor and the throttle position sensor are both pretty new.....
> 
> thanks