Martijn van Duijn > wrote in message
...
> Hi,
>
> After seeing a decrease in mileage on my 96 Ford Taurus wagon (~ 24 to
> ~20 mpg. 140.000 Mi odo), I decided to take a look at my oxygen sensors
> as a possible culprit.
> I read out their voltages during idle when warm using my Elm ODB
> scantool, and plotted them.
>
> http://www.duijn.info/OxygenSensor.jpg
> x in seconds, y in volts
>
> It looks to me that something is fishy in Bank 2, but the signal does
> not look like the typical error modes that I read about (sluggish, low,
> flat). Bank 1 looks like the examples I saw for good sensors.
>
> I am not experienced enough to make a statement on these curves, but am
> hoping they ring a bell with one of you people. Does it look familar, is
> my data aquisistion simply too slow (I don't have a scope, sorry...).
> The peaks in sensor 2/2 also look like they don't belong there. Is the
> fuel injection acting up due to bad info from sensor 1, and too rich a
> mixture making its way through the cat? The traces were recorded
> separately to improve time resolution...
>
> If a sensor is indeed bad, is it doable to replace it with just basic
> tools, or is it best left to a pro?
>
> Thanks for any thoughts you may have.
>
> Martijn

1/1 appears to be fine. 1/2 should have a relatively flat output though
which appears to indicate that the catalytic converter on that bank isn't
doing much.

2/1 is either dead or genuinely indicating a very weak mixture. However if
the mixture really was very weak then 2/2 wouldn't be displaying higher
readings so it appears that 2/1 really is dead. Until you replace 2/1
there's little point in trying to decide if that converter or 2/2 are ok or
not.

Sensors just unscrew so if you can handle a spanner I very much doubt you
need a 'pro' to do it for you.
--
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)