How to Clean the Oxygen Sensor in a '98 Mazda 626

The 1998 Mazda 626 base model came with a 2.0-liter four-cylinder engine and a five-speed manual transmission. The 2.0-liter engine has two oxygen sensors that relay how much oxygen is in the exhaust gas as it passes through the exhaust system. If your vehicle is equipped with a California-mandated emissions system, there is one oxygen sensor at the top of the exhaust manifold and one just below it. If your 626 is equipped with federal-mandated emissions, your oxygen sensors are located below the exhaust manifold and behind the mid exhaust-mounted catalytic converter. Because of their delicate internal components, oxygen sensors cannot be cleaned and must be replaced.

Instructions

Park the vehicle on a level surface and set the parking brake. Lift the vehicle hood and support it with the hood prop rod. If you are replacing the front oxygen sensor, skip to Step 3. Allow the engine to cool completely before continuing.

Lift the front of the vehicle into the air with the floor jack and place the jack stands under the front subframe. Lower the floor jack until the vehicle rests securely on the jack stands. Remove the floor jack.

Follow the oxygen sensor pigtail from the base of the oxygen sensor to the connection at the vehicle wiring harness. Squeeze the locking tab and separate the oxygen sensor pigtail from the harness.

Spray penetrating oil around the hex head base of the oxygen sensor and allow it to soak to the threads at least one to two minutes. Install the oxygen sensor socket over the oxygen sensor so that the pig tail sticks through the opening in the socket. Rotate the oxygen sensor counterclockwise about 30 degrees.

Remove the sensor socket and spray the sensor base with penetrating oil. Allow the penetrating oil to soak into the sensor threads for at least two minutes. Install the sensor socket and loosen the oxygen sensor with the ratchet. If the sensor begins to bind, loosen and tighten the sensor repeatedly until the oxygen sensor has been removed.

Coat the new oxygen sensor threads with the nickel anti-seize compound if there is not already an anti-seize coating on the threads. Thread the oxygen sensor into the exhaust piping by hand. Install the oxygen sensor socket onto the oxygen sensor and tighten the sensor to between 22 and 36 foot-pounds with the torque wrench.

Connect the pigtail to the vehicle wiring harness. Pull on both plastic connectors to ensure they are properly connected.

Lift the vehicle off of the jack stands with the floor jack. Remove the jack stands from under the vehicle and lower the vehicle to the ground.