"Dave Baker" wrote

> > 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

> 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.

1/2 is pretty flat... (it's below 1/1, not beside it).
Of course, that's assuming Martin labelled the charts correctly.

> 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.

2/1 (top right) is all over the place, with 2/2 (bottom right) following close behind.

Sticky/plugged injector, misfiring plug, bad wire, vacuum leak?

> Sensors just unscrew so if you can handle a spanner I very much doubt you
> need a 'pro' to do it for you.

Yup.