How to Check for Clogged Catalytic Converter

A significant quantity of harmful pollutants flow via the catalytic converters (CATs), which can eventually result in their blockage. 

If this occurs, a blocked catalytic converter will be unable to effectively convert these exhaust emissions, resulting in their accumulation in the combustion chamber and a decrease in engine performance. This problem requires immediate identification, else your engine could entirely stop working. 

Here are a few signs of a failed catalytic converter:

Illuminated Check Engine Light 

One of the most noticeable indications of a clogged catalytic converter is a lit check engine light. 

If you see that the check engine light is illuminated, you can utilize an OBD scanner to ascertain if the catalytic converter is the source of the issue. 

Difficulty Initiating the Vehicle

When a catalytic converter becomes blocked, it results in a significant quantity of smoke flowing through the exhaust system. This could result in frequent stalling or make it challenging to start the car. 

If the catalytic converter system has a significant obstruction, your engine is likely to make irregular sounds and may take a few seconds to start. 

Slow acceleration 

Decreased engine performance is one of the most noticeable indications that your catalytic converter might be obstructed. If you observe your car experiencing jerking, stalling, and difficulty ascending steep hills, it is probable that poor combustion is the culprit.

What is the reason for that occurrence?

A malfunctioning catalytic converter hinders the passage of exhaust gases through the converter and out of the exhaust pipe. 

Initially, you might consider the possibility of insufficient fuel pressure. In actuality, noxious gases become trapped in the combustion chamber, resulting in incomplete combustion, reduced acceleration, engine performance, and increased engine lag. 

The odor of sulfur and decaying eggs

A functional catalytic converter transforms noxious gases into a less detrimental discharge.

In what manner? 

Once gasoline reaches a functional catalytic converter, it converts pollutants such as hydrogen sulfide into sulfur dioxide, which is odorless. A blocked catalytic converter is unable to effectively handle the sulfur emissions, resulting in a foul odor resembling rotten eggs. 

Engine Misfires

When the catalytic converter becomes blocked, harmful gases that are trapped in the engine become heated to the point where they can ignite. 

This ignition causes the engine to misfire, leading to damage to important engine parts over a period of time. If you observe your engine misfiring, it is advisable to promptly reach out to a specialist.

Low Fuel Efficiency 

If your car has a major obstruction in the catalytic converter, it will negatively impact your fuel efficiency and gas mileage. 

A blocked catalytic converter might result in increased exhaust accumulation in the engine, which decreases the availability of fresh, combustible oxygen necessary for optimal operation.

When the engine gets a less amount of oxygen, it needs to exert more effort to reach a higher speed. The additional weight not only reduces your fuel efficiency but also exacerbates the blockage in the converter. 

Unsuccessful Vehicle Emission Test

Many states mandate that automobile owners undergo annual vehicle emission tests. A catalytic converter is the primary component responsible for ensuring proper exhaust gas emissions. 

Therefore, if your catalytic converter is obstructed and unable to effectively process hazardous gases such as carbon monoxide, it is probable that your vehicle will not pass an emissions test. 

Now you comprehend all of the important symptoms. 

Once you observe one or more of these indications, you may choose to diagnose the issue with the catalytic converter.

Let’s discover how to accomplish that. 

How to Identify a Blocked Catalytic Converter (3 Techniques)

There are three methods to determine a defective catalytic converter:

Testing the vacuum 

Prior to doing this test, you will require a vacuum gauge. 

Here are the instructions to perform a vacuum test:

Place the automobile in neutral or park.

Attach the vacuum gauge to a direct vacuum line, such as the direct intake manifold. 

Start the automobile and let it idle until it reaches the optimal operating temperature. 

The vacuum gauge should display a measurement of 18-22 Hg. 

Begin increasing speed and let the automobile reach approximately 2500-3000 rpm.

The vacuum gauge reading should decrease before reverting to the previous level. If it requires a significant amount of time to decrease, it is probable that you have a faulty catalytic converter. 

Temperature Check

To conduct a temperature test, you will require any kind of thermometer, such as an infrared or kitchen thermometer. 


Consider using a catalytic converter cleaning to remove any blockages in the component. A catalytic converter cleaner can also cleanse an oxygen sensor or spark plug. This can be used to remove any carbon buildup.





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