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Today’s insight is about the catalytic converter. I have learnt that a bad catalytic converter, if not realized early enough, can force you to replace your car engine. A clogged catalytic converter might not even send errors to your ECU.

I started experiencing certain symptoms sometimes last month. My vehicle used to be so fast but suddenly it became slow. I tried a diagnosis on my own but there were no errors. I then decided to seek mechanical help from a very reputable garage but guess what? They couldn’t identify the problem. There were no errors and the engine compression tests were perfect!!. They advised I change the spark plugs and I even suggested they service the gearbox. We used the best ATF and CC but nothing changed.

Today I decided to troubleshoot the vehicle by myself once again. All my sensors were perfect. I decided it was time to remove my exhaust system and test for leakages. My noticeable leakages at all. I decided to go further and check the Catalytic converters and guess what? That is where the whole problem was! The catalytic converters were clogged both banks.

So I found a seller online, I bought them and had them welded. After fixing the exhaust system with the new Catalytic converters, the vehicle is now perfect.
So, bad catalytic converters have drained the pockets of some people to a point where some have replaced car engines with new ones while others have sold their vehicles believing that the problem is irredeemable.

Before making such mistakes and doing expensive repairs based on guesswork, always check your catalytic converter. Below are symptoms to look out for just to know where the problem lies.

Symptoms of a failing Catalytic Converter

Oxygen Sensor Code

In case of an issue with your car’s Catalytic Converter, your engine will throw an O2 sensor code indicating that the oxygen level and exhaust emissions are outside of their limits.

High Fuel ⛽ Consumption

Due to improper combustion of the fuel as a result of a clogged exhaust, your car engine will underperform because it will need to work harder to generate the same amount of power. Therefore, a bad catalytic converter will most often cause a higher fuel consumption.

Increased Emissions

Increased emissions is one very obvious symptom of the bad catalytic converter. When a Catalytic Converter is failing, it won’t perform it’s do its task of reducing emissions as expected. So, you will notice a high level of carbon emissions and this is a signal there could be an issue with your exhaust system. A bad Catalytic Converter can damage the entire exhaust system if not fixed promptly.


When the catalytic converter is clogged, the air flow of exhaust fumes is restricted resulting to the engine’s air-fuel mixture getting richer (too much fuel, leading to unburnt fuel).

The combustion of this excessive air-fuel mixture causes an odor smell like burnt sulfur (like that of rotten eggs). If you notice this smell (some of it sometimes seeps into the vehicle), then it is an indication that your Catalytic Converter has a problem that needs quick fixing.


This is usually the first symptom of a failing Catalytic Converter. The catalytic converter can overheat. Very rich fuel mixture in the oil tank causes the engine to misfire. Raw fuel entering the Catalytic Converter can melt the CC’s components.

Loud Noise

Catalytic converters are frequently stolen due to the precious metals inside. Converters contain small amounts of platinum, rhodium and palladium, all of which have value for metal dealers. So, don’t fully trust your mechanic or neighbor. When the CC goes missing, it creates a vacuum and this will result in your car making lots of racket.

What causes a catalytic converter to fail?

There are two primary reasons why Catalytic Converter fails:


When it becomes fouled or plugged from too much oil. When an engine starts to wear out and more oil ends up getting burned in the combustion chamber, the residue ends up getting trapped in the Catalytic Converter. This plugs the tiny passages. This eventually renders the catalyst useless.

Excessive heat

If an engine has an engine management system failure, such as a bad oxygen sensor, plugged injectors or dirty MAF sensor, the engine computer can get a bad air-fuel mixture signal. If this causes the engine to run too lean, or in some cases, too rich, this can generate more heat in the Catalytic Converter than it was designed to handle. The excess heat causes the Catalytic Converter to glow cherry red and it eventually ends up getting destroyed.
In majority of cases, you will notice warnings in the form of a DTC (Diagnostic Trouble Code), which will cause a CEL (Check Engine Light) to light up 🚨. Never ignore that Check Engine Light.


Catalytic Converters are quite expensive to replace. Therefore, proper diagnosis is crucial before you make a blunder of purchasing a new one. If you notice the symptoms above yet other components like the spark plugs, sensors and filters are okay, then try checking the Catalytic Converter. The problem might be right there.

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By Editor Car Xperts Reloaded

Car Xperts Reloaded is run by highly experienced auto-engineers and auto-bloggers with many years of motor industry workings and passionate about all things related to cars and automotive. Our goal is to provide readers with useful and interesting information, so that they can make informed decisions when purchasing or maintaining their cars. We are open to suggestions and feedback, and excited to be part of the automotive blogging community!

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