O2 sensor question - how it works

[nacelp]

> Do you mean wall wetting?

Shoot me for a dam typo........

> Isn't that likely to have evaporated after 50 revs or so?

No, not on all engines.

> How does reversion apply to a steady-state over-run condition?

Cause before you went into an over run condition, you have have been in a
range where it was occuring, and maybe WET'd the walls.   You can be amazed
by actually working on a car after a over run and shut down, water droplets
form every where under the butterflies, and sometimes the WALLS are still
WET with fuel.  Let it heat soak for a few minutes, and you'll never see
it...

> Sorry to ask so many dumb questions...

> >PCV valve
> >Charcoal canister.

> Certainly worth taking into account.
> But I thought they were controlled from the ECU nowadays.
> Not like it's a 1980's antique. :-)

I didn't realize you were limiting this to specific years.  You have to
purge things completely for a 0'ing of calibrating a O2 devise, 0, as in
free state.

> Even then; the charcoal cannister won't usually discharge until
> there's a significant throttle opening on the older systems (usually
> determined by manifold vacuum) otherwise the idle becomes unstable
> due to excess fuel vapours from the canister. I'm not sure exactly
> how that applies to over-run. There's even more manifold depression
> on over-run so any vacuum-servo valve won't be opening.

Think about it, you have very high vac., with the throttle closed at high
rpm,  much more so then at idle.  The CCP solenoids are cheap, and with
dust/use/age, the will "bleed some"
>
> Anyway, it would make sense not to feed any fuel at all as the spark
> is often suppressed on over-run as well; it'd just screw up your HC
> emissions.

We were talking about WB O2s.

> >Are all contibuting to emissions even thou the fuel may be off during
> >overrun.

An engine is an air pump.   Fuel on or off, spark on or off, if the engine
is turning, it's pumping air.  Throw anything into it, and it effects it's
emissions.
Grumpy
>
> --
> Real Name: Bernd Felsche
>     Email: nospam.bernie at perth.DIALix.com.au
>      http://www.perth.dialix.com.au/~bernie - Private HP
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