this is probably why the 2.1 waterboxer engine has a 3 wire oxygen sensor,
two of which are for a heating element in it.
You can easily retrofit a 3 wire oxygen sensor to your 1.9 engine.

the current for the heater element in the sensor can come from the main
relay power output, or maybe even from the ignition wire .........on this
very nice 83 Westy I'm getting ready to put up for sale.........I think
someone before me wired it that way - power source for the sensor heating
element is right from the black ign wire at the coil.   Possibly not the
best, but seems to work.  I don't know how many amps the heating element
draws but not that much I wouldn't imagine.

well, how much does the fuel injection ECU depend on the O2 signal ?
I suspect it's like the top 20 % of fine fuel trim.........
since they'll run plenty nicely enough with the 02 disconnected or worn out.
Other opinions /theories welcome.
I figure it 'fakes it' until a useful 02 signal starts happening again.

it would be a useful experiment for you to compare the performance up and
down hills, etc. of a 3 wire 02 with that of your single wire 02 sensor. A
single wire 02 sensor is pretty old fashioned , btw.
86 and up vanagons have the 3 wire.
all 90's era Subaru's have a 3 wire, etc.
Scott
www.turbovans.com
----- Original Message -----
From: "pickle vanagon" <greenvanagon@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, August 29, 2008 3:59 PM
Subject: When the O2 sensor cools down...

> ...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