Catalytic Converter Overheating – Causes, Consequences, & Fixes

Every internal combustion engine produces harmful exhaust fumes during combustion, and the car exports these toxic fumes into the atmosphere through the exhaust system. However, there’s a need to prevent these toxic fumes from creating environmental health issues.

Auto manufacturers design the catalytic converter to fight the harmful fumes in the exhaust gas to convert it to less toxic gas before releasing it into the environment. Over time, the catalytic converter can clog or overheat due to issues within the engine.

In this article, you’ll learn the causes and consequences of catalytic converter overheating issues and how to fix them. Read on.

driving with a bad catalytic converter

Why is my catalytic converter overheating?

Luckily, you’ll have catalytic converter failure symptoms when the cat con fails to help you track and address the issue at the early stage. Like every other car system failure, there are a few reasons why the catalytic converter overheats.

Restricted flow

A clogged catalytic converter will prevent the normal flow of exhaust fumes exiting the vehicle through the exhaust pipe. If this is the case, the backpressure in the engine will be increased, invariably causing overheating on the cat con.

Overworked engine

A normal combustion process happens when an oxygen and fuel mixture is consumed completely under precise conditions. If there’s a failed or malfunctioning engine component, like a failed MAP or MAF sensor, the engine may try to compensate by adjusting the air-fuel pressure in the system. This will most likely cause the engine to overwork itself.

Engine misfire

Anything that causes too much hydrocarbon (HC) or engine misfires will eventually cause the catalytic converter to overheat. Issues with the spark plugs, distributors, plug wires, ignition coils, and mass air flow can cause engine misfires, leading to overheating on the catalytic converter.

Defective O2 sensor

The O2 sensor monitors the oxygen content in the exhaust streams and forwards the information to the car computer or ECM using a voltage signal. If the O2 sensor becomes faulty, it’ll send inaccurate information to the engine control module. Then, the ECM will work with the information and send more fuel or air into the combustion chamber, depending on the false information it receives from the defective O2 sensor.

If the computer sends more fuel, some will leave the combustion chamber unburn and burn in the catalytic converter. The unburnt fuel from the combustion chamber will cause overheating and melting of the substrate in the cat con.

Leaking injectors

Leaking fuel injectors will lead to too much fuel in the combustion chamber. As a result, some fuel will be left unburnt. The unburnt fuel will exit the combustion along with the exhaust fumes and cause overheating in the catalytic converter.

Of course, you may be wondering, can a catalytic converter cause the engine to overheat? Yes, a clogged cat con can cause the engine to overheat. A clogged catalytic converter will create pressure buildup, resulting in engine overheating.

Read Also: How to Find Catalytic Converter Scrap Value By Serial Number

how to fix overheating catalytic converter

What happens when a catalytic converter overheats?

As explained earlier, an overheating catalytic converter could mean you have a clogged cat con, resulting in a backpressure in the system. This means the catalytic converter may not allow exhaust fumes to exit the pipe. The effect is that, as the engine is not breathing out properly, it’ll cause severe engine problems.

Here’s what I experienced some months ago. A customer towed his vehicle to my garage, complaining that it doesn’t climb hills and doesn’t even travel more than 40mph when cold. The issue gets worse when the vehicle gets hot.

When I diagnosed the vehicle, my scan tool couldn’t read what was wrong with the vehicle. I tried another scan tool, which pulled several error codes like P0300, P0420, P0430, and many others. When fixing anything, my rule is to start with the most common possible causes.

So I diagnosed the fuel system, the upstream and downstream O2 sensors, and the ignition system, and everything is in good condition. After going back and forth, I start the vehicle and leave it idle for a while. After an hour, I noticed the exhaust system had turned red hot, which means the catalytic converter was seriously overheating due to blockage.

I turned off the vehicle and let it cool. After replacing the clogged catalytic converter, the vehicle starts running as it should.

Therefore, overheated catalytic converter symptoms or what happens when it overheats include loss of engine power, unresponsive gas pedal, misfiring, excessive heat underneath the car, and red hot catalytic converter.

How to fix an overheating catalytic converter

The first step on how to fix the overheating catalytic converter is to detect the root cause of the problem. Catalytic converters are designed to last the vehicle’s lifespan or at least ten years. So if they fail before then, there’s likely a problem within the system.

You have to diagnose the vehicle and ensure other system components are working as they should. When diagnosing the vehicle, check the spark plugs, O2 sensors, mass air flow sensors, and fuel injectors. If any of these components are faulty, fix them before heading to the catalytic converter.

If any of them is the root cause and you unclog the cat con, the lousy component will still clog it in the nearest feature. After addressing the root cause, disconnect the catalytic converter and inspect it. If it’s not long gone, you can fix the cat con without replacing it. But if you have a severe blockage, the only feasible solution will be to delete the cat con or replace it with a new one.

Final Words

Driving with a bad catalytic converter will cause your car to lose power. If the leading cause of the problem is lousy spark plugs, it may cause the engine to overheat, which can blow the head gasket. Luckily, Catalytic converter overheating issues will display the check engine light on the dashboard to warn you of an underlying issue.

So, once you see that panic-inducing light on the dash, diagnose the vehicle to figure out the root cause and rectify it. The light could mean the cat con is bad, or there’s something else wrong in the engine.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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