RE:0xygen Sensor....HELP

[Russ Southerlin <russell.s.southerlin@lmco.com>]

Bob wrote:
Trying to take voltage readings on the Oxygen Sensor.
Have (3) wires from the sensor.... White, White, & Black.
The Black is the one.As the engine idled (hot) I get readings from less
than 100mv to 750mv.
(moves between these 2 readings as it idles.)

I usually connect to mine at the ECU input connector (pin 33 is + and
34-).  This way you will be checking the wiring to the ECU and you can
monitor while driving. 

I usually see less fluctuation at idle than what you are seeing. I
usually get a slow fluctuation between 400-600mV at idle.  The
fluctuations coincide with the duty cycle (DC) fluctuations of the OXS
Freq. valve.

The ECU is trying to keep the oxygen sensor at exactly 500mV which is
ideal air mixture. In order to do this it varies the DC to the OXS F/V. 
If your oxygen sensor voltages are fluctuating this much I would bet
that the DC is also making big swings.  I think this is a symptom of a
bad or old and tired oxygen sensor.  I think there is a spec. on how
much the DC is allowed to change.

The OXS F/V makes that clicking sound that can be heard under the hood
at idle.  If the DC is making big swings the tone (frequency) of the
clicking sound will change and even stop if the DC goes full rich/lean
trying to keep the O2 at 500mV.

Yes it is working but maybe not in the most ideal way.

One other important thing - CHECK FOR VACUUM LEAKS.

Russ
87 5KCSTQ
Littleton, CO