'86 CGT oxy sensor

[urquattro]

Wrongo!  Audi was well entrenched into 3-wire OXS' in 1986.  Apologies for
being a bit abrupt, but please remember that someone reading the post might
have believed you to be correct and installed a 1-wire OXS in their car to
save $$$.  Unfortunately, the other thing that Audi did was to mount the OXS
a bit farther downstream in the exhaust ... depending upon the heater to
ensure proper operation of the OXS.  When I bought my '85 4kSQ the car never
really ran well ... when I dropped the cat (yes that's where the OXS is
mounted on this car!) I found the PO had installed a one wire OXS in place
of the requisite 3-wire.  After chasing down a set of replacement heater
wires (thanks Chris Semple!) I was able to fit a universal 3-wire
replacement ... and the car runs like a champ!

While you are right that the ECU will ignore the OXS until the engine warms
up, if you install a 1-wire in a car which is supposed to have a 3-wire the
ECU will start reacting to the OXS when the engine warms up ... but the OXS
will not be operating properly as it is not at the correct temperature!  Get
a 3-wrie replacement Craig ... you will definitely see a difference in the
way your engine runs ... and the fuel economy will probably improve as well
...

Steve Buchholz
San Jose, CA (USA)

> in '86 audi was using unheated sensors, so it's prolly correct. The extra
> unused connector you see is the CIS OXS duty cycle for setting the mixture
> and CO level. Even if you put a 3-wire in, the ECU won't do anything w/
the
> signal till the thermoswitch triggers. So unless you swapped ecu's too,
you
> wouldn't benefit. The poor mileage is prolly combination of things...bad
o2
> sensor, spark plugs, fuel filter, fuel injectors, engine compression,
vacc.
> leaks, etc.
>
> try replacing the cheap stuff first and inspect the whole thing
> carefully...good luck.
>
> -ameer
>
>
> At 10:11 PM 10/2/00, you wrote:
> >With all this oxy sensor talk, I know my '86 CGT is in need of a new one.
It
> >currently has a one wire sensor in it now. I noticed that while this 1
wire
> >sensor plugs directly into a single socket plug on the factory harness,
> >there is a 2 wire socket on the same harness that is unused. Does the '86
> >CGT take a 3 wire heated sensor, or is the 1 wire one correct? I've
looked
> >in the family album, and its inconclusive. I am hoping replacing this
sensor
> >will correct the horrible idle problems and the poor gas mileage (~12 mpg
> >according to the trip computer). TIA.