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Old 01-04-2013   #36
mike100
 
Join Date: Feb 2011
Location: San Marcos CA
Posts: 1,786
Default Re: Emissions Testing

The last time my car smogged real clean was 10 years ago, but after replacing the O2 sensors, the NOx really came down this time and it runs clean again. The fuel mixture band for the formation of the fewest oxides of nitrogen is so narrow and it does require accurate 02 readings. I was surprised that the sensors foul with age more than mileage (20-30k miles on the somewhat more dirty tests).
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