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Apr 26, 2022 · When Should You Replace Your O2 Sensor? Oxygen sensors are not among the maintenance items that need to be replaced regularly, such as oil and air filters, so they typically are replaced only...
Oct 12, 2022 · Whenever the check engine light is on, and you experience any symptoms, you should immediately take the vehicle to an auto shop and replace your sensor. Generally, a new sensor will last anywhere from 60,000 to 90,000 miles. Drive safe and do your yearly maintenance!
- Overview
- Illuminated Check Engine light
- Decreased fuel efficiency
- Sulfuric or gasoline smells from the exhaust
- Black smoke from the exhaust
- Poor motor performance while driving
- Strange pinging or knocking sounds
- Rough idling
- Stalling engine
- Very high emissions levels
Your Check Engine light is on, your car is guzzling gas like crazy, and is that smoke coming out of your exhaust? The culprit might just be one of your O2 (oxygen) sensors—small, spark plug-sized machines that measure the amount of oxygen leaving your engine through the exhaust. When they get dirty or damaged, your engine can’t tell how much air is inside of it compared to the amount of fuel, leading to a variety of possible problems. In this article, we’ll walk you through all the symptoms of a bad O2 sensor and the mechanics behind them so you get them replaced before your engine gets damaged.
Bad O2 sensors may lead to excess fuel in your engine, causing decreased fuel efficiency and possibly black smoke or sulfuric smells from the exhaust.
Over time, your engine may also start stalling, rough idling, or making pinging and knocking noises as a result of incorrect air-to-fuel ratios.
Eventually, a bad O2 sensor will cause very high emissions or even the complete failure of your catalytic converter.
Bad O2 sensors affect your engine and trigger the Check Engine light.
When your O2 sensors start to go, they can’t measure the levels of oxygen in your exhaust accurately. This means the engine control module won’t know to correct any air-to-fuel imbalances in the engine. This can lead to a wide variety of engine problems, any of which can turn on the light.
The Check Engine light doesn’t monitor your O2 sensors directly. It can only sense engine problems that may be caused if they start to go bad.
The light may also come on if your sensor is just dirty rather than faulty. In this case, you or a mechanic might simply have to
Faulty O2 sensors can cause your engine to burn more fuel than needed.
Have you been spending more on gas or making more frequent trips to fill up the tank than usual? The culprit may be your O2 sensors. If they can’t monitor the air-to-fuel ratio in your combustion cylinders, the mixture may become “rich” (fuel-heavy), meaning your engine is using more gas than it needs to function.
This results in noticeably poor fuel economy (and an equally noticeable hit to your bank account).
Schedule an appointment to inspect and replace your oxygen sensors as soon as you notice decreased fuel efficiency (or
if you’re car-savvy, but the sensor location on certain makes and models may make this difficult to do at home).
The cost of O2 sensors
Pungent, excess fuel can build up in the engine from bad O2 sensors.
Notice if you smell sulfur, a rotten egg-like smell, or plain gasoline when you turn on your car or stand outside it while it’s idling. This is the excess fuel in the engine burning off, and could indicate your oxygen sensors are not measuring the lack of air in the combustion cylinders.
This smell is typically accompanied by black smoke coming out of the exhaust.
If your vehicle has reached this point, it’s probably because more than one O2 sensor has failed (most vehicles have 2 oxygen sensors per exhaust pipe).
Black smoke comes from improper combustion from low oxygen levels.
Oxygen is what your engine uses to burn fuel. When there’s too little, the combusting gasoline creates black smoke that travels out through your exhaust pipe. Normally, a functioning O2 sensor would tell the engine control module to adjust the air-to-gasoline ratio, but when it malfunctions, the engine continues operating with too much fuel.
Besides the Check Engine light, black smoke is the only visual symptom of a faulty oxygen sensor.
Black smoke is also a sign that your emissions levels are way too high (a problem that O2 sensors are designed to help prevent).
Bad sensors can cause misfires, lurching, poor acceleration, or jerking.
Notice if your vehicle “fights” you when you start the engine or as you’re driving. If you’ve been driving with bad oxygen sensors for a long time, the imbalance of air and fuel can degrade your engine’s overall performance. In severe cases, you may even experience power surges or a complete loss of power on the road.
Noises from beneath the engine may be caused by too much air.
When your O2 sensors can’t monitor the air-fuel mixture, the mixture may run lean (meaning there’s more air than fuel). This leads to a buildup of carbon in the combustion chamber, which can cause pinging, knocking, or rattling noises (particularly when you turn the ignition on).
Your engine may run extra fast when parked or idling.
Normally, the RPM rate for an idle engine is under 1,000. If there’s excess fuel in the engine due to bad oxygen sensors, though, the RPM may spike beyond 2,000 or even 3,000. There are multiple reasons your engine may have a rough idling problem, though, so this alone isn’t a surefire sign of a bad O2 sensor.
Rough idling may also be accompanied by engine misfires caused by poorly timed combustion intervals.
You may have driven too many miles with dirty or faulty sensors, especially if you have an older vehicle. Most O2 sensors last for 30,000 to 50,000 miles (48,280 to 80,460 km), or about 3-5 years for the average driver.
Rough idling caused by bad O2 sensors can cause the engine to stall.
The engine may misfire when you turn the ignition or shut down completely since it can’t sustain the right amount of power and fuel to function properly. This typically only happens if you’ve been driving with bad oxygen sensors for a long time and the engine has sustained some damage as a result.
If you fail an emissions test, bad O2 sensors are a likely culprit.
Your oxygen sensors are a major component of your emission control system, and without them, you’ll likely develop a noticeable imbalance of fumes in the exhaust. Ask your mechanic to run a diagnostic test if you fail a mandatory emissions test—there are several reasons your emissions may be out of whack, but your O2 sensors are some of the first things to check.
Aug 24, 2010 · As a rule, the service life of oxygen sensors in most 1996 and newer vehicles with OBD II should be 100,000 to 150,000 miles or more — assuming no problems that could cause the O2 sensors to fail prematurely.
May 25, 2022 · How do you know when your car needs an O2 sensor replacement? Here are the signs of a faulty oxygen sensor to look out for!
- Braden Carlson
- Senior Writer, Social Content
Apr 8, 2020 · As a thumb rule, you may consider replacing your oxygen sensors every 65,000 to 90,000 miles, if your vehicle is less than 15 years old. This will reduce pollution and keep your car engine running efficiently. If your car is older than 15 years, it is best to replace the O2 sensors every 50,000 to 65,000 miles.
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What is an oxygen sensor in a car?
Aug 13, 2021 · An oxygen sensor, or an O2 Sensor, helps your car maintain exhaust and emission levels. Learn more about what signs you should be looking for when it is time to replace your oxygen sensor.
