Re: O2 sensors

["Graydon D. Stuckey" <graydon@apollo.gmi.edu>]

On 20 Apr 1996, Joe Yakubik wrote:

> As part of the 60k check it says to replace the o2 sensor.  Audi's price was 180

Bosch designs the regular O2 sensors to last 60,000 miles.  They go 
downhill very fast after that, although some last alot longer.  That is 
the reason for the 60,000 mile recommendation.

> replace them as a matter of course, but test them when they do the
> exhaust/emissions inspection.  Because my car is exempt from the full-up
> inspection I asked if he could test mine and he said "No, if your idle is good,
> and your MPG is good and your car runs okay, then your o2 sensor is okay.  When
> you have these problems then bring it back." He then said if I really wanted he
> could test it, but it would waste my money.  I like this guy.

Yep, this is basically good advice.  As for testinf them, I haven't 
really seen a definitive test for an O2 sensor.  You wo8uld really need a 
calibration gas of known composition to test the O2 sensor's output.  If 
you put an analog 0-1 volt volt meter on the output, you can see how the 
O2 sensor responds, adn assuming the ECU is doing its job properly, you 
will see a characteristic up/down pattern.  If then you see a change in 
this pattern, you may be able to make the prognosis that the O2 sensor is 
"going."  I use a 10 led air/fuel ratio meter to monitor the O2 sensor, 
adn to see how my engine is running.  It isn't perfectly accurate at 
extremely rich or lean settings, but at stoichiometric mixtures, it is 
dead accurate.  (This is another whole discussion in which there are 
many people more qualified than I)

HTH

Later,								
Graydon D. Stuckey								
graydon@apollo.gmi.edu								
Flint, Michigan   USA
'86 Audi 5000 CS Turbo Quattro, GDS Racing Stage II