Check Your O2 Sensor

We talked before about oxygen sensors going bad. A bad oxygen sensor will think there is not enough fuel in the air-fuel mixture and add more. The result will be too much fuel for the amount of oxygen and not all of it can be burned. The extra unburned fuel will be wasted with the exhaust. Remember that your engine is an air breather.

This video compares a bad and a good oxygen sensor to show the difference. The two sensors are given time to warm up. Then a rag is wet with brake cleaner. Because the brake cleaner is combustible, the sensor treats it as fuel. The good sensor indicates the presence of fuel (full rich) as long as there is still brake cleaner in the rag. The bad sensor after a short time shows full lean. The bad sensor thinks there is far too much oxygen relative to fuel even though the situation is the opposite. You do not want this to happen in your car!