Most car manufacturers don't recommend a specific interval for oxygen sensor replacement. Those that do recommend replacement at about 50,000 miles. Always check the owner's manual for the specific interval appropriate to your car.
A malfunctioning O2 sensor can manifest itself in many ways - surging and/or hesitation, a noticeable decline in fuel economy, increased tailpipe emissions and premature failure of the catalytic converter. Note that sensor operation can be affected by other engine problems, such as erratic fuel control or a plugged air cleaner. Engine coolant or oil entering the combustion chambers can damage the sensor, as well. And sometimes they just plain get old and lazy.
Testing for a defective sensor can be accomplished with a scan tool. So check for any DTCs indicating O2 sensor problems. On OBD II vehicles, if the downstream sensor is very active, the powertrain computer could set a code, but the problem may not be with that sensor. The catalyst could be defective or overloaded with fuel, the cause being a defective upstream sensor in the manifold. Any routine maintenance on an engine-replacing plugs, repairing or replacing cracked vacuum hoses, cleaning fuel injectors, etc.-also should include a scan test or dedicated test of the oxygen sensors.
When replacing an O2 sensor, always follow the manufacturer's recommended procedure, which will invariably include torque specifications and call for the application of some type of antiseize compound on the threads.
If you don't replace the sensor regularly, you could end up with inferior performance and economy and the prospect of damaging the catalytic converter. Whatever the case, don't overlook this component as one of the most important engine performance service items.
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