Most vehicles manufactured after 1980 contain engine oxygen sensors as part of the emissions control system to help the engine run efficiently and keep harmful emissions low. These sensors constantly measure oxygen content inside the exhaust manifold and compare it to the air outside the engine. When the sensor fails, the vehicle has poor engine performance and higher emissions. Mechanics recommend oxygen sensors be replaced at least every 100,000 miles as part of regular maintenance. Numerous symptoms point to a faulty oxygen sensor.
An obvious decrease in gas mileage is the main symptom of a faulty oxygen sensor.
Rough engine idling is another symptom of a bad sensor, as is an engine that "misses" or runs irregularly.
Loss of acceleration power also points to a faulty oxygen sensor.
A faulty oxygen sensor can cause the vehicle to run at higher temperatures than normal. It may even cause your car to overheat.
Because a faulty oxygen sensor cannot accurately measure air/fuel concentrations, this can result in higher toxic emissions. Many times, failure to pass an emissions test is caused by a faulty oxygen sensor.