Where is the o2 sensor located on a 1994 Mercury Cougar 6 cyl?

The usual location for oxygen sensors on Cougars is in the exhaust pipe just after the catalytic converter.

• Why do we have O2 sensors on cars

All new cars are now fitted with oxygen sensors and since around 1980, most cars have had them. They have been relevant since the advent of engine management systems which are computers that help the car run efficiently. Before these computers were commonplace, the oxygen output was irrelevant. So we have the sensors now to give the on-board computer as much data as possible in order for the car to run smoothly.

• What data do the sensors produce?

When the car is burning fuel, the ideal situation is to have what is referred to as the 'perfect' ratio of air and gasoline in the process. If there is not enough air then fuel will be left over after combustion. This causes a lot of pollution. If there is not enough air then the engine will perform poorly. It can also damage the car. The sensors monitor these ratios so that the computer can make adjustments to get closer to the perfect level.

• How do the sensors work?

The process involves a chemical reaction that generates a voltage. The voltage is what the computer looks at and interprets. The car needs the sensors to be operating at all times because the perfect ratio can depend on things like air temperature and load. These are changeable so the sensors have to be operational at all times.