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Can a Bad O2 Sensor Cause Smoke? (All You Need to Know)

Unusual smoke is a clear indication of something wrong with a car. Most car owners tend to ignore the issue until the problem gets bigger. Do you suspect your O2 sensor for a smoke? 

This article will discuss if the O2 sensors can cause smoke and what you can do to fix it.

Can a bad o2 sensor cause smoke?

O2 sensors can cause smoke from your car. The sensor is a vital part of fuel injection, and if there is an O2 sensor problem, the air and fuel ratio goes wrong, which can cause smoke from the exhaust. However, it’s not the only sign of a bad O2 sensor, and different causes can also cause smoke.

Smoke is usually a bad sign for car owners, and they must solve that issue quickly to avoid more complex problems. There can be many reasons for unusual smoke in the car, but does a broken O2 sensor cause smoke? 

The answer is yes. But also remember that smoke is only one of some symptoms of bad O2 sensors. Moreover, other problems can produce smoke.

But don’t worry. By observing other symptoms, you can understand if the O2 sensor is responsible for the problem. We will discuss them in the latter part of this article.

But to get a clear idea about if the O2 sensor causes smoke, why it happens and how to fix it, let’s go through how the O2 sensor works. We will keep things quick and simple.

Oxygen sensors are one of the essential components of modern fuel injection systems. It works to give every necessary information from catalytic converter efficiency to fuel economy to the main computer. 

O2 sensors produce their signals by observing the oxygen ratio inside and outside the exhaust tributary. In simple words, the O2 sensor senses the excess oxygen inside the tributary. 

The leftover or used oxygen is directly connected with the burned fuel. That means that more energy is being burned if more oxygen is used, while excess oxygen indicates that less fuel is burned.

When there is a lot of leftover oxygen, that is referred to as a lean condition, while less oxygen is called a rich condition. 

The O2 sensors provide that information to the central computer, and the computer uses that information to control the correct fuel injection, fuel efficiency and many more. 

The sensor can understand the O2 usages by comparing the O2 inside and outside the tributary. It creates a voltage that indicates O2 difference inside and outside. 

If there is more oxygen leftover inside, the sensor produces less voltage which is way under half a volt (A lean condition) 

On the other hand, if more oxygen is used, the sensor produces more than half a volt, near 1 volt. The sensors make 0.50 volt when the oxygen ratio is ideal.

The computer receives those signals and controls the fuel injection to avoid lean or rich conditions.

The O2 sensor’s outer part is also crucial for sensing O2 outside, so make sure not to use oil, grease or silicone-based products over an O2 sensor.

 It was a simplified explanation of the O2 sensor function, but in reality, the system is much more complicated and advanced.

Now let’s move on to how a bad sensor can cause smoke. When the O2 sensor is bad, it can’t send the correct information about the fuel burn. That means the car loses its ability to control the fuel and air injection system. 

When that happens, the car can inject less fuel than necessary which causes low efficiency, backfire, idling, or injecting more fuel than needed, which drives smoke from the car. 

This issue reduces the car’s performance, wastes fuel, and hurts the environment. You will notice smoke from the following part of a car if you have a bad O2 sensor.

From exhaust:

When you have a bad O2 sensor, you will notice smoke from the exhaust pipe.

Will 02 sensor cause these smoke?

A faulty O2 sensor can be pretty problematic for car health and efficiency. The O2 sensor tells the car computer how much fuel to inject for how much air. This system is essential, as fuel-burning needs a different amount of air depending on the altitude and the environment.

The fuel injection becomes automatic and out of control if the system goes wrong. If the engine injects more fuel than necessary, the extra fuel will come through the exhaust pipe. Different colored smoke can indicate different types of O2 sensor issues.

Black smoke:

A bad O2 sensor can cause black smoke. It happens when the fuel is not burned correctly.

Blue smoke:

Bad O2 sensors can cause blue smoke. But it is a rare condition, and it’s sometimes hard to differentiate between white and blue smoke. Blue smoke from the exhaust pipe indicates the engine uses excess fuel than necessary.

White smoke:

White smokes are more common when the O2 sensor is not working correctly.

3 reasons why does a bad o2 sensor cause smoke

A bad oxygen sensor causes smoke from the exhaust pipe. But what actually causes the smoke? Check the following reasons.

Misjudging the fuel requirement:

The O2 sensor sends the correct information about the fuel required to the computer so the computer can signal to use the right amount of fuel. When this system fails, smoke is produced.

Wrong air and fuel ratio

Too rich fuel burn conditions can cause smoke from a car. That means that when the injector injects more fuel than the available air, the amount of O2 in the air is not sufficient for burning the fuel. 

As a result, carbon monoxides are produced, a key component of black smoke. White smoke also contains carbon monoxide.

Uncompleted burning of fuel

A problematic O2 sensor can cause more fuel usage. Excess fuel can come out with smoke when that happens.

How to tell which oxygen sensor needs to be replaced?

If you have a car more than seven years old and did not change the O2 sensor, maybe it’s time to check the O2 sensor condition. A new O2 sensor can last about 6-10 years or 60-100 thousand miles. But sometimes problems can happen earlier. 

If you notice low performance, stalling, backfire, unusual smoke etc., you should check your O2 sensor if it is okay or not. Find out the detailed symptoms in the next section.

How can you tell which O2 sensor is bad?

Some symptoms indicate that your O2 sensor is not working correctly. Check out the following points.

Low performance:

Bad O2 sensors can cause performance in your car. What happens when the car uses less fuel than necessary. That results in trouble accelerating, idling, backfire etc. If those symptoms match your car, read the following points to be sure.


Low performance and smoke are two significant symptoms of the bad O2 sensor. That means that if the engine uses less fuel, that causes low performance, and if the engine uses more fuel, that causes smoke. Those both can also happen together.

Low fuel efficiency:

O2 sensor issues can also result in low fuel efficiency as the car computer have no control over the fuel usage.

Unusual engine sounds:

A Bad O2 sensor disturbs the timing of fuel injection, which can cause unusual sounds.

Engine light:

If there is any problem with the O2 sensor, the engine light turns on.

How to fix a bad o2 sensor?

Usually, if an O2 sensor gets bad, there is no way to fix it, as it has complicated parts. But don’t be hopeless. Sometimes the sensor can get clogged from inside or outside, which can cause the O2 sensor to work poorly. Cleaning and reinstalling can solve the issue sometimes. 

Here is a DIY step-by-step guide to cleaning and fixing the clog.

Find the oxygen sensor:

Jack up your car and try to find the location of the oxygen sensor. The sensor should be connected to the exhaust pipe on the passenger side. You may need to unbolt some bolts and disconnect some weirs.

Remove dirt:

Now, use a wire brush to remove dirt from the tube-like the end.

Soak in the gasoline:

Now, take some gasoline in a jar and soak the tube-like end in the gasoline overnight.

Reinstall the sensor:

Reinstall the sensor as it was the next day. Set the sensor with a bolt and connect the wires correctly. The sensor should start working again if dirt and clog were the problems.

Final Thoughts

If you notice unusual smoke in your car, that can be caused by a bad O2 sensor, but you must look for other syndromes to be sure if the O2 sensor is bad or if there are other problems. Take your car to professionals if you don’t have much idea about cars, as often issues can be pretty complicated.