what does to voltage go to? does it drop way off?  During engine
braking it should be quite lean which should show as low voltage on
the narrowband o2

Jim Akiba

On Fri, Aug 29, 2008 at 6:59 PM, pickle vanagon <greenvanagon@gmail.com> wrote:
> ...what happens?
>
> I rigged up a air/fuel mixture meter (just a voltmeter coming off the O2
> sensor) a few months back.  On our recent trip across the country, we
> obviously spent some time driving in hillier country than we usually do, and
> I noticed something funny.  While engine braking down a long hill, all the
> clear air coming through the exhaust system, while obviously hot, is
> apparently not quite as hot as the sensor needs to be, so that it will
> eventually cool down to the point where it no longer provides good output
> and behaves like it does right after startup.  After driving for a little,
> it warms up again and output is normal.
>
> I'm wondering what the ECU does during this stage.  Does it know to start
> ignoring the oxygen sensor if it thinks its output doesn't make sense?  Or
> does it just keep chugging along, thinking everything is peachy, and
> consequently send too much or too little fuel as the oxygen sensor fails to
> react dramatically enough to the changes in ratios of the exhaust gasses?
>
> -Wes
> 1.9l westy
>