O2 Sensor question
 

I replaced the O2 sensor in my 930 this afternoon and noticed that the tip on the old one is covered in a white powdery substance (wipes off). Is this an indicator of a lean condition?


-Wade
'88 930 Slant Coupe

Found some info on this. The article mentions that the white powder is apparently silicone. Not sure if this is a bad indicator or not but I just recently passed emissions...hmm

-Wade
'88 930 Slant Coupe

Source: http://www.sjmautotechnik.com/20vo2tst.html

O2 SENSOR PROBLEMS

"One problem that affects the O2 sensor operation is contamination or poisoning by silicone, this shows up as a fine white powder on the tip of the sensor and will reduce the voltage output of the sensor when the mixture is rich, and this will cause a loss of fuel economy and increased CO and HC emissions. You may also see a negative voltage developed under lean operation when the sensor is poisoned by silicone. This poisoning causes the sensor to see a lower proportion of Oxygen.

The slots in the tip of the O2 sensor can also get partially clogged with carbon which will increase the response time. This will cause the O2 voltage change to slow way down, taking 3-4 seconds to go up and down, instead of changing in less than a second. This slow response can cause a varying idle speed and varying idle mixture. The exhaust gas Carbon Monoxide (CO) reading will not be steady at idle when read by an exhaust analyzer. This can also cause some light surging under light acceleration with the engine cold and when fully warmed up under cruise conditions."