How To Unclog A Clogged Catalytic Converter | The Ultimate Guide

David Lawrence

David Lawrence

A catalytic converter is more important than any individual can assess. It is important to know how to unclog a clogged catalytic converter and ensure that your car is running smoothly and fast. 

How to Unclog a Catalytic Converter

The simplest way to unclog your catalytic converter is to pour the catalytic converter cleaner into the fuel tank. Start driving your car at 2500 RPM for almost 30 minutes. If you drive long enough, the catalytic converter cleaner will move around the tank to clean it.

Suppose you are also experiencing some clogged catalytic converter symptoms. In that case, we are here to tell you some simple ways to see whether it is actually clogged and how to unclog a catalytic converter in no time. 

You came across this article because you were looking for information on how to clear out a clogged catalytic converter. When you first start driving a vehicle with an internal combustion engine, the catalytic converter in your vehicle may likely become clogged at some point in the future. 

This raises the question: why is this happening? We are going to cover this in this article and explain in detail the functions of a catalytic converter in a car. We are also going to highlight the cheapest way to fix the catalytic converter when it is clogged, ensuring that this repair does not cost too much to you! 

So stay tuned to the article and learn all you need to about clogged catalytic converters.

What are Catalytic Converters?

At the moment, more than 90 percent of vehicles on the road are powered by internal combustion engines (ICE), and it is highly unlikely that this pattern will alter before electric vehicles become the standard in the automotive industry.  However, this often leads to the formation of hazardous chemical compounds that are harmful to the environment, which is also one of the reasons why this method is less than ideal and not appreciated. 

Catalytic converters are the tools that help prevent these cars from damaging the environment irreparably. Catalytic converters use rare metals to alter the chemical composition of the gases that are being produced in order to neutralize the harmful byproducts that they produce. 

Because of the growing environmental consciousness that can be found all over the world, this component of the exhaust system is one of the most important advancements in the entire history of the automobile. It is helping the automobile industry stay afloat with this technology today. 

Therefore, the primary function that catalytic converters serve is to convert potentially hazardous exhaust gases into others that are of a quality that allows them to be safely discharged into the atmosphere. Because of all of the smoke that blows through the exhaust system, it is only a matter of time before it becomes clogged.

Why Do Catalytic Converters Become Clogged?

Although it may be helpful to assume a clogged catalytic converter is the issue and get it inspected, sometimes the problem isn’t solely due to blockage. Other engine-related complications could contribute to the converter’s damage.

It’s crucial to distinguish between a worn or chemically damaged catalytic converter and a blocked one.

When a converter fails chemically without being clogged, the check engine light or malfunction indicator lamp (MIL) will signal a problem.

If the chemically failed but unclogged converter is not the light-off catalytic converter – the one closest to the engine and monitored by an O2 sensor – the engine may not display any signs of trouble. In other words, clogged catalytic converters aren’t the only cause of poor performance. A catalytic converter can still lose efficiency over time, even without physical blockage.

Therefore, it’s vital to recognize the warning signs and symptoms to watch for.

Problems Of  Having a Catalytic Converter Clogged

There are many expensive and rigid problems that a user may face while dealing with a catalytic converter clogged due to a variety of reasons. The most important problem that can arise from a clogged cat is an increase in the exhaust backpressure that it can produce. The limitation in exhaust flow that the clogged cat causes may cause the engine to face several performance issues. 

Additionally, a damaged catalytic converter can not only lead to your vehicle failing an emissions test but also harm nearby components, resulting in costlier repairs. Several factors can cause the premature deterioration of your catalytic converter, such as:

  • Catalyst performance issues
  • Catalysts can be susceptible to contamination from substances like antifreeze and oil, both of which can cause damage.
  • Engine problems

To better comprehend these issues, we’ll provide an overview of some of the most common and time-consuming problems that cars face due to clogged catalytic converters.

Bad Engine Performance 

This happens due to back pressure. Sometimes, even when there is a large obstruction, the engine will start, and it will keep running for a few minutes, but it will finally shut off. 

Bad Fuel Economy 

If your car’s catalytic converter becomes blocked, it will impair the vehicle’s ability to function properly. This could result in reduced speed and overall performance, as well as decreased fuel efficiency.

Numerous other issues can stem from a clogged catalytic converter; however, these are the most significant.

These symptoms can indicate a blocked converter, and if your car exhibits any of them, it’s advisable to have the engine inspected promptly or consider replacing the converter.

Best Time to Replace Your Catalytic Converter 

If the catalytic converter is clogged with debris, replacement is necessary. Although products exist to clean catalytic converters, their reliability is questionable. The only solution to address the issue is to replace the obstructed converter.

Even in states without emissions testing requirements, it is against federal law to remove a catalytic converter and substitute it with a pipe.

Hence, unless it can be repaired, you must replace the blocked converter through authorized dealers as soon as you’re informed of the problem. Adhering to this guideline helps you avoid potential trouble.

Clogged Catalytic Converter Symptoms

In order to ensure that you have good engine health, you need to look out for symptoms that lead to a catalytic converter clog. For a brief analysis, here are some of the symptoms that need to be looked out for. 

Check Engine Light is on 

It is very obvious that you have a problem if the catalytic converter in your vehicle is clogged. In the event that the catalytic converter in your car becomes obstructed, the onboard sensors will sound an alarm and notify you of the situation.

The most prominent of them are the check engine light and the O2 sensors.

The check engine light will turn on if there is an issue with the vehicle. You will be able to notice a fault code associated with the catalytic converter if you have an OBD scanner that is compatible with your car and can read the code.

Emissions Test Fail

If the “Check Engine” light is on, the next logical step is to have an emission test performed on the vehicle. If the test fails, this provides irrefutable proof that the catalytic converter is clogged. This is due to the fact that the catalytic converter is an essential component of the emission control system in your vehicle and must be maintained in proper operating order.

A failed emissions test is an evident indication that the catalytic converter is blocked with debris.

Increase in Overall Emissions

If the catalytic converter has been harmed in any way or if it has become clogged with debris, there is a possibility that it will no longer perform in the proper manner. As a consequence of this, the engine of the car will produce a greater quantity of emissions.

It should come as no surprise that the primary purpose of the catalytic converter is to lessen the number of hazardous pollutants produced.

Noisy Car

There is something known as a ‘honeycomb’ inside the catalytic converter, which needs to be checked. If the catalytic converter is not properly maintained, the “honeycomb” that is found inside of it can become worn and break apart into fragments. This will produce a ratting and irritating sound when you turn on the engine. 

If you are not able to figure out the weird sound that your car is making, you can have a friend hit the accelerator pedal while you try to ascertain whether the rattling sounds are coming from the catalytic converter or somewhere else. This will also prevent any misleading symptoms of your car from diverting you. 

Engine Fire 

A clogged catalytic converter is a significant issue for vehicles, as efficient fuel combustion in engines requires a significant amount of oxygen. The engine overheats and may even misfire as a direct result of the limitation in airflow because of the accumulation of unburned gas that has not been consumed.

Discoloured Housing

If the catalytic converter’s housing has altered its color, be it blue or any other hue, there might be a blockage causing the converter to overheat. If your engine is underperforming, unburned fuel can infiltrate the catalyst.

This combustible blend ignites from the converter’s inherent heat, leading to the interior material melting and creating further obstructions. This situation is highly hazardous for the car and could potentially result in a fire.

Should you suspect any malfunction in your catalytic converter, refrain from operating your vehicle. This precaution can help prevent additional damage to other engine components.

Over Fueling 

An engine is said to be overfueled when it is supplied with more gasoline than it is able to burn off. Keeping the catalytic converter in good condition is one way to avoid this problem. Because of the higher levels of back pressure, the engine will need to exert more effort in order to successfully release the exhaust.

Acceleration Lag  

If you notice delays when accelerating or a decrease in power when driving in steep terrain, but all of the other components, such as spark plugs, filters, sensors, and so on, are in good shape, it is possible that the catalytic converter is faulty. Get it checked as soon as possible. 

How to Check a Clogged Catalytic Converter 

If you notice any of the above clogged catalytic converter symptoms, you should have some information about the effects of such an issue on your car. There are some specific ways to check for the same. This is important because there can be some other reasons too why a catalytic converter may be clogged. This will also help you find the cheapest way to fix catalytic converter

One of the simplest ways to do this is to put your hand close to the end of the exhaust pipe and then have someone boost the RPM of your car to 2000. This will allow you to determine whether or not your catalytic converter is clogged. If there is very little exhaust produced, there is a good chance that the catalytic converter will become blocked. 

However, for a more nuanced check, you can also follow the methods below 

Use a Vacuum Gauge 

 A vacuum gauge can be used to check the vacuum reading when it is inserted inside the engine. The vacuum reading on a motor that has been properly maintained should only fall for a brief period of time before rising to a level that is slightly higher than that of the engine when it is in its idle state. 

A reduction in a vacuum that occurs when the engine speed is increased but does not return to the level it was at when the engine was idling is suggestive of a catalyst that has become clogged. If continuing to raise the RPMs leads the needle to move in the opposite direction, we can deduce that the engine speed is already at its optimum level. 

Check the Backpressure 

Vehicle back pressure varies based on factors such as age, manufacturer, and model. Typically, a standard engine should not need more than about 1.5 pounds of pressure when idle. While some engines can handle higher pressures, it is generally advisable to aim for 1.5 PSI or lower. To measure back pressure, low-pressure gauges are required.

A digital manometer is recommended for the most precise readings. After removing the check valve, you can connect your pressure gauge to a secondary air injection system if your vehicle has one.

Obtaining more reliable results may be possible by attaching the check valve to the exhaust system before the converter.

It is crucial to note that back pressure can be measured using a vacuum gauge, not a pressure gauge, in addition to assessing the vacuum. Connecting a vacuum gauge to the manifold, rather than the exhaust, is a significantly simpler procedure.

Alternatively, you can install the pressure gauge by drilling a hole in the exhaust pipe right before the catalytic converter.

This method is another way to attach the gauge and is the best option if you’re concerned about the oxygen sensor in an older car. Parameters from a scan tool, such as manifold absolute pressure (MAP) and calculated load, can also serve as potential back pressure indicators.

However, these processes can be overwhelming for someone short on time. If you can identify the symptoms mentioned above, you can simply call a technician to check the converter for you.

Cheapest Way to Fix Catalytic Converter

Here, I will tell you the steps to clean and unclog the catalytic converter without removing it.

  • Add fuel to a container and use a catalytic converter cleaner. Most cleaners are designed for either gasoline or diesel engines, but some are compatible with both.
  • Make sure your fuel tank contains at least 15 liters of fuel. Pour the suggested quantity of cleaner into the fuel tank.
  • Start the car and begin driving. As you drive, the cleaner will disperse throughout the exhaust system, providing a thorough cleaning. Refer to the cleaner’s label to determine the optimal driving duration for the best results.
  • Typically, driving at 2500 RPM for 30 minutes should be sufficient to unclog the catalytic converter in most cars. However, avoid excessive driving, as it may cause your car to overheat, leading to additional problems.


Below are the frequently asked questions on how to unclog a catalytic converter. Let’s dive deep to understand more.

What is the actual cost to fix a catalytic converter? 

On average, fixing a catalytic converter will cost you around $950 to $2500, including parts and labor costs.

Will premium gas help clean the catalytic converter?

Premium gas which is generally more on five than regular, won’t clean the catalytic converter, but it prevents the cover from being clogged in the first place. However, as mentioned in the article, there r a y reason for a catalytic converter to be clogged, so the fuel that pours into your vehicle might not have anything to do with it.

Can a catalytic converter unclog itself?

As a general rule of thumb, no. The only way a catalytic converter can itself is through sustained driving at high RPMs. You’re driving the car at a certain speed for a long period, meaning you have to put a significant amount of effort into your part. Thus, a catalytic converter unclogging itself is a pipe dream.

What will a clogged catalytic converter do?

A clogged catalytic converter will make your car jerk forward and stall during acceleration. A clogged catalytic converter is like a clogged artery for human beings. It will become difficult for your engine to build up pressure.


A clogged catalytic converter is a headache for automobile users. In this article, we have explained all the necessary details regarding a clogged catalytic converter. Through this, you can easily learn how to unclog a catalytic converter in no time. 

We have also explained the symptoms of a clogged catalytic converter in detail. Moreover, since many of these symptoms also arise due to other engine problems, we have provided the information on double-checking whether it is the catalytic converter or something else causing the problems. 

David Lawrence
About the author
David Lawrence
David grew up among mechanics and off-road enthusiasts, gaining deep knowledge in car mods, off-roading techniques, and automotive engineering, making him a trusted 4x4 expert.

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