oxygen sensor readings

[Eric Ekberg]

So how do I go about using the signal as a vague indicator of the A/F ratio?
Average it?  Over how long?
I'm not planning on doing any fueling with this, just another gadget to display
on the LCD.  Really I'm just looking for good,bad,danger, etc.
>From what you're saying, Assuming normal operating parameters with a good
running engine, would 800-900mV indicate 14+ to 1?  Would 450mV be a good
mixture?
thanks for your help,
Eric

GRUMPYNOMO wrote:

> Don't think of the O2 sensors indications as rich or lean.  Think of them as
> "all oxygen used up" (around 900mv) and "some oxygen left over after
> combustion" (around 100mv).
> This may seem picky but if you see a low voltage and assume the engine is
> running lean, you may be looking at incomplete combustion or a miss.
> More significant yet is a jagged waveform at the high (rich?) side which might
> look like a cylinder that is lean but could be 'puff' of EGR gas (not rich)
> from a faulty valve.
> Sensors vary but popular pattern is a variation from 0mv to 100mv at the low
> side to  800mv to 900mv at the high side with an average of 450mv.
> Oxygen sensors will never stay at the mid point.  They will flip-flop from
> seeing no spare oxygen to seeing some oxygen remaining in exhaust stream.
> They are incredible devices: so rapid and sensitive that, with a good scope,
> you can identify vacuum leaks and bad injectors.  They are a very
> underutilized diagnostic tool.