Can a Bad Catalytic Converter Cause Smoke? (Explained)

A catalytic converter is one of the most essential parts of a vehicle. It converts the toxins and pollutants in the exhaust gas to less toxic byproducts. If the catalytic converter is defective, there will be serious issues in the vehicle

So, you might be wondering if a defective or clogged catalytic converter can cause smoke. You might also wonder why your car’s catalytic converter is smoking. Let’s find the answers to all your queries regarding smoke caused by a bad catalytic converter.

Can a bad catalytic converter cause smoke?

A bad catalytic converter can cause dark exhaust smoke to release from the tailpipe. Due to a clogged catalytic converter, the exhaust gas gets trapped inside the engine which eventually causes smoke. The catalytic converter will also cause smoke if unburnt fuel is directly released on it.

A catalytic converter transforms the toxic components in the exhaust gas into less toxic elements like carbon dioxide and water vapor. It prevents the original toxins released by the engine to mix with the air and damage the environment. 

The transformed exhaust gas is then released from the catalytic converter through the tailpipe.

If the catalytic converter is defective, the exhaust gas will trap within the engine. The airflow in the engine will also reduce massively if the catalytic converter is clogged, which will increase the engine’s temperature. 

As a result, if the vehicle has a bad catalytic converter, it will definitely cause smoke.

Different types and colors of smoke can be produced due to a bad catalytic converter. Let’s find out if a defective catalytic converter can cause black smoke, blue smoke, or white smoke.

Black smoke:

If a catalytic converter is clogged or defective, it will definitely cause black smoke. When the catalytic converter is faulty, the exhaust gas gets trapped inside the engine. 

The exhaust gas is normally dark colored, and when it is trapped inside the engine this gas burns up, making the gas much darker. As a result, when a vehicle’s catalytic converter is faulty, the exhaust gas will come out in the form of black smoke. 

Blue smoke:

When the fuel is burnt in the combustion engine with a mixture of air and gas, blue smoke is formed. If the catalytic converter is defective, exhaust gas can’t escape from the car normally and the airflow will be non uniform. 

As a result, the fuel will get burnt with air within the engine, forming blue smoke.

White smoke:

If unburnt fuel falls directly on the catalytic converter, white smoke will come out of the converter. This usually happens when the airflow to the engine is restricted due to clogged catalytic converters.

How does a bad or clogged catalytic converter cause smoke?

A bad or clogged catalytic converter causes smoke due to various reasons. One of the main reasons for the formation of smoke on the catalytic converter is the trapped exhaust gas in the engine. 

It also occurs due to the increased back pressure because of the clogged catalytic converter.

The catalytic converter transforms the toxic elements in the exhaust gas into less harmful byproducts. The transformed exhaust gas is released into the environment through the catalytic converter. 

When the catalytic converter is clogged, the exhaust gas won’t be able to come out of the engine which will increase its temperature. As a result, due to the increased temperature, the catalytic converter will start to smoke.

A defective catalytic converter will massively enhance the backpressure within the engine. The increased back pressure will cause the engine to malfunction and overheat. 

Due to the overheating engine, the exhaust gas will also heat up and when it comes in contact with the catalytic converter it also heats up and causes smoke.

The airflow to the engine will reduce significantly due to a bad catalytic converter. If there is low air in the engine, the fuel-air ratio in the engine won’t be perfect. As a result of the low air to fuel ratio, the engine will malfunction and will cause smoke.

The smoke that comes out of the catalytic converter can be in various forms and colors. Black smoke, white smoke, and blue smoke can be caused due to a bad catalytic converter.

Why is my catalytic converter smoking?

Your catalytic converter can smoke for numerous reasons. It is very important to know the reasons behind why your catalytic converter is smoking so that you can address the issues as soon as possible. 

By doing so, you can also prevent any severe damage to the catalytic converter and your engine.

High back pressure:

When the backpressure within a combustible engine increases massively the engine starts to malfunction. This occurs because of a defective or clogged catalytic converter. 

When the backpressure increases, the exhaust gas won’t go through the converter in the right way, which will cause the catalytic converter to smoke.

Fuel enters the exhaust system:

The fuel can sometimes remain unburnt due to worn out spark plugs and defective pistons. The unburnt fuel is released by the car through the exhaust system. 

When the fuel is released through the exhaust system it goes through the catalytic converter which isn’t made for transforming liquid, so it starts to smoke.

Trapped exhaust gas:

Trapped exhaust gas can cause the catalytic converter to smoke. The exhaust gas can get trapped inside the engine due to a bad catalytic converter. 

When the exhaust gas gets trapped, the catalytic converter doesn’t get anything to convert, and as a result, smoke comes out of the catalytic converter.

Can a bad catalytic converter cause smoke under the hood?

A bad catalytic converter can cause smoke under the hood. When the catalytic converter is defective or clogged, the exhaust gas will get trapped in the engine and some of it will come out through the hood.
This smoke under the hood caused by the catalytic converter is usually dark black and it smells like fuel. You can fix this issue by replacing the catalytic converter. 

If you repair the catalytic converter without replacing it and even if the smoke stops, the car will still have bad gas mileage.

Does a new catalytic converter smoke?

A new catalytic converter rarely causes smoke. If the brand new unit smokes, it is usually due to burning the oil used in its body while manufacturing. 

A brand new catalytic converter will not smoke due to the fact that it won’t get clogged which traps the exhaust gas and causes smoke. The new unit won’t also be defective as a result, the back pressure won’t be high which causes the converter to smoke.

How to fix my catalytic converter smoking?

Fixing the catalytic converter smoking issue is not as difficult as it may seem to you at the beginning. However, you will have to do it with proper caution and by following proper methods to prevent damaging the exhaust system and the engine.

Have a look at how you can fix your car’s catalytic converter:

Replace worn out spark plugs:

A catalytic converter can smoke if unburnt fuel from the engine directly gets released into the catalytic converter. This usually occurs when the spark plugs of the engine are worn out or defective. 

Due to defective spark plugs, the engine won’t be able to ignite the fuel properly and a good amount of fuel will remain unburnt. By replacing the worn out spark plugs you will prevent the fuel from getting into the catalytic converter and prevent it from smoking.

Use better quality fuel:

The engine malfunctions when the quality of the fuel is poor and there are impurities in the fuel. If the engine malfunctions, fuel will get through to the catalytic converter directly which will cause smoke. 

As a result, by using better quality fuel you can prevent the catalytic converter from forming smoke.

Replace the catalytic converter:

A bad catalytic converter usually gets clogged. Due to the clog, the exhaust gas gets trapped inside the engine. The trapped exhaust gas usually increases the engine’s temperature and smoke forms and comes out from the catalytic converter. 

You can prevent the catalytic converter from smoking by replacing the old catalytic converter with a new one.

Final Thoughts

A defective or bad catalytic converter usually causes smoke. The clogged catalytic converter does not let the exhaust gas get released from the engine, as a result, smoke is produced. If unburnt fuel gets into the catalytic converter, smoke will also form and get released from it.