The O2 sensors in your Mercury Villager help to monitor the air flow coming out of your engine. These exhaust gases will tell the O2 sensor how much unburned fuel is left in the exhaust gases so that the Mercury's ECU can adjust the air to gasoline ratio and improve fuel economy as well as horsepower, while reducing emissions. After approximately 60,000 miles, you'll need to check and replace your O2 sensors if they are faulty. You may be able to stretch the replacement interval to 100,000 miles, but when the check engine light comes on and a diagnostic test shows a faulty O2 sensor, it's time to replace them both.
Let the Mercury Villager cool down. If you've recently run the engine, you'll need to let the engine and exhaust system cool down before you can work on it. Failure to do so will result in serious burns.
Place the jack under the front jack point located behind the radiator. Jack up on the vehicle and place jack stands underneath the Villager. Then, lower the Villager onto the stands.
Locate the O2 sensors on the exhaust system. They will be near the catalytic converter. One of them is located before the converter and the other, after it. Remove the electrical plug running to the O2 sensor. This is a plug-style connector that pulls out by pushing down on the retaining clip and pulling the connector off the O2 bung.
Remove the O2 sensor with a socket wrench and O2 removal tool extension. Turn the O2 sensor counterclockwise to remove.
Coat the threads of the new O2 sensor with anti-seize and insert the sensor. Make sure that you tighten the sensor until you feel resistance, and do not over tighten it.
Reconnect the electrical wiring running to the O2 sensors and lower the Villager to the ground.
