How to Install Oxygen Sensors on a 1998 Mercury Mountaineer

The oxygen sensors in the exhaust system of your 1998 Mercury Mountaineer help the fuel system regulate the amount of fuel burned by the engine. If the oxygen sensors fail, you may notice a drastic decrease in the fuel mileage of your truck. The 1998 Mountaineer is equipped with four oxygen sensors. There is a sensor on each side of both catalytic converters. Buy replacement sensors from an auto parts retailer.

Things You'll Need

• Jack
• Jack stands
• Oxygen sensor socket
• Ratchet

Instructions

1. Lift the truck with a jack to support it with jack stands. Locate the oxygen sensors on each side of the dual catalytic converters in the exhaust system.

2. Disconnect the wiring harness at the top of the oxygen sensor. You can pull the connector apart by hand. Remove the oxygen sensor with an oxygen sensor socket and ratchet.

3. Thread the new sensor into place by hand to prevent cross threading. Torque the sensor to 30 pound-feet with your torque wrench. Connect the wiring harness by pressing the electrical connection together.

4. Repeat the process for the remaining sensors you want to change. Raise the truck slightly and remove the jack stands. Lower the truck to the ground.

References

• "1998 Mercury Mountaineer Factory Service Manual"; Ford Motor Company; 1997