Left: The oxygen sensor screws into the exhaust manifold
I sometimes use this website to post mechanical information, as I am very much a fan of the concept of shared knowledge. Those who do not wish to be bored with auto repair, please continue on to the next post.
My 1996 Saturn SL has had some stalling and idling problems that have gradually worsened in the last few months. I used my philosophy of "repairing the least expensive related parts," and changed the spark plugs, plug wires, and fuel filter, but the problems continued.
I moved next to the oxygen sensor, which is also known as the O2 sensor. After replacing this sensor - which measures the concentration of oxygen remaining in exhaust gas to improve the efficiency of the combustion process - my car no longer stalled and the rough idle disappeared.
Left: the used oxygen sensor after removal from the manifold
The process of removing an O2 sensor is quite simple, and I suspect that one could continue wearing one's flashy Air Jordan shoes whilst changing said part. Here are the steps you can follow to replace an oxygen sensor:
1. If you have a twin-cam engine (it will say so on a big label on the valve cover), you will need to make sure to purchase the correct sensor. There is also an oxygen sensor that screws into the exhaust system near the catalytic converter, but this is usually a special-order part. The front oxygen sensor that screws into the manifold is typically the first of the two sensors to wear out. Most auto stores stock this oxygen sensor.
2. Allow the engine to cool. It is best to change this sensor in the morning after the engine has cooled overnight.
3. The auto parts store will try to sell you a special O2 sensor wrench, but you can remove the old oxygen sensor with either a box wrench or an adjustable wrench. Just be sure to disconnect the wiring first and do not over-torque the wrench, or you will end up snapping off the sensor in the manifold (very bad). The wiring on the O2 sensor usually clips into a connection, and you have to depress the plastic tab to connect/disconnect the wiring.
4. Apply a light amount of grease on the threads of the new sensor, making sure to wipe off the excess. This will prevent the sensor from rusting or becoming corroded to the manifold.
5. Screw the new sensor into the manifold. If you do not have a torque wrench, go no more than a quarter-turn past hand tight. Again, you do not want to strip out the new sensor in your manifold and have to re-tap it.
6. Reconnect the electrical wire to the assembly.
7. Fire up the engine and see if you now have a fine running automobile. If not, curse the $60 you spent on an oxygen sensor and restart the diagnosis process. Hint - you might next want to check your MAP sensor.