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How to know if your catalytic converter is out of order

You have suspected something wrong with your vehicle for a while. An unusual noise, a different behavior, in short, something is wrong. As a far-sighted and responsible driver, you don't wait for a breakdown, but you start looking for answers. When a warning light on the dashboard comes on, it's never a good sign. You inspect the technical manual and venture under the bonnet, but it's hard to find something when you don't know what you're looking for, right ? Krosfou, DPF, and catalytic converter's specialist helps you and teaches you how to detect a catalytic converter failure. How do you know if your catalytic converter is out of order ? Here is our checklist of points to check and alerts not to be overlooked.

Damaged catalytic converter : possible causes

Your catalytic converter may be defective for several reasons. Depending on the symptoms and suspicious noises you detect, the causes may be mechanical, thermal, or caused by the part clogging.

Mechanical causes 

The catalytic converter is a fairly robust part, but it is located under the car and as close to the ground as possible. It can therefore break due to a shock, even if it is small or insignificant for you, such as a speed bump passing a little too quickly.

The honeycomb structure is made of ceramic, which is a breakable material. In case of breakage, you will hear a saucepan noise at the front of the car when you idle. In such a situation, you have no choice but to have your catalytic converter changed.

Thermal causes

The catalytic converter is effective from a certain temperature. If the temperature is too low, the chemical reaction does not take place. If the temperature is too high (when there are too many polluting gases to be treated in particular) the part deteriorates. The ceramic honeycomb structure can melt under the effect of too much heat and render your catalytic converter unusable. It seems unbelievable that the ceramic can melt, but this happens when the engine settings are unright. The fuel is completely unburned in the combustion chambers. The overflow then drains out through the exhaust line, of which the catalytic converter is a part. Again, the replacement of the part is unavoidable.


You may not know it, but the catalytic converter's role is to filter the engine gases and transform them. In this way, the gases released into the air we breathe every day are less harmful. A filter means also residue, which inevitably leads to the catalytic converter becoming dirty and clogged. This is the most frequent cause of a catalytic converter malfunction, and it is the one we will discuss in more detail below. Replacement is not systematic, and you can prevent this by cleaning the part.

How do I know if my catalytic converter is out of order: the symptoms

Clogging is the most common problem with this type of part. Here are the points that should attract your attention:

  • The activation of the engine light. This is a signal that you must not ignore because it necessarily indicates a malfunction.

  • The loss of power to your engine. It rises slower in revolutions and gives the impression of running out of breath.

  • A smell of sulfur (some poets even speak of the smell of rotten eggs).

  • Dark smoke coming out of the exhaust. When the catalytic converter no longer plays its role, the emission of polluting gases becomes more important, which colors the smoke.

  • More frequent stalling. 

  • Over-consumption of fuel.

You can rejuvenate your part by cleaning it, as long as the honeycomb monolith is still in good condition.

What a faulty catalytic converter reveals

As you have now understood, a damaged catalytic converter is very often the tree that hides the forest. This type of breakdown is the consequence of other problems that will undoubtedly ruin your life and increase the bill enormously

Overheating may be caused by :

  • Faulty lambda sensors. These sensors measure the amount of air and fuel before and after passing through the catalytic converter. The information is sent to a computer that adjusts the fuel and air quantities for optimal engine operation.

  • Faulty spark-plugs, one of the many reasons why your engine light will come on.

  • A faulty fuel injection system. Excess fuel will irreversibly damage the honeycomb, destroying the precious metals that cover it.

A clogged catalytic converter is the sign:

  • Poor quality fuel;

  • Engine problems.

In conclusion, you should never drive with an out of order catalytic converter. First of all, you are putting your car at risk and exposing yourself to a lot of problems at the same time:

  • Premature wear and tear on your vehicle;

  • A heavy fine in the event of an inspection;

  • Expensive repairs, and more repairs than if you had reacted in time.

Do you want to know if your Catalytic Converter is Bad ? Do you want to know if your DPF is clogged ?

Posted on 08/28/2020 by 2020 0 3125

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