What Makes the Catalytic Converter Malfunction?

What Makes the Catalytic Converter Malfunction?
A catalytic converter is a crucial component in a vehicle's exhaust system designed to reduce harmful emissions from the engine's exhaust gases. However, while catalytic converters effectively reduce emissions, they’re also sensitive to certain contaminants and conditions.  
Structural damage, exhaust build-up, use of improper fuel, and even engine tuning can damage the catalysts. What happens then? You guessed it – the check engine light appears. In this blog post, we'll explore the factors contributing to catalytic converter malfunctions and look over possible solutions to keep your vehicle running smoothly and eco-friendly.  

What’s a catalytic converter?

The catalytic converter contains a substrate made of a ceramic or metal material coated with catalysts, typically made of precious metals like platinum, palladium, and rhodium. It significantly reduces air pollution and improves air quality by converting harmful carbon monoxide (CO), hydrocarbons, and nitrogen oxide pollutants into less harmful substances before they are released into the atmosphere.

How does it work?  

A catalytic converter works through a series of chemical reactions within its core structure – the catalyst substrate. It resembles a honeycomb-like structure that provides a large surface area for the catalysts to interact with the exhaust gases passing through it. Here's how the catalytic converter works:  
  • Carbon monoxide (CO) oxidation – when exhaust gases containing carbon monoxide (CO) flow through the catalytic converter, the catalysts facilitate the oxidation reaction. Oxygen (O2) from the exhaust gas combines with carbon monoxide to form carbon dioxide (CO2), a less harmful gas.   
  • Hydrocarbons (HC) oxidation – hydrocarbons (unburned fuel molecules) are another component of exhaust gases. The catalysts within the catalytic converter help promote oxidation reactions that break down hydrocarbons into carbon dioxide (CO2) and water (H2O).  
  • Nitrogen oxide (NOX) reduction – they’re a group of pollutants formed during high-temperature combustion processes. The catalysts in the catalytic converter facilitate a reduction reaction that converts nitrogen oxides back into nitrogen gas (N2) and oxygen (O2).  
The catalytic converter must operate within a certain temperature range to achieve optimal performance. It must reach a minimum operating temperature, typically around 400 to 600 degrees Fahrenheit (200 to 300 degrees Celsius), to efficiently catalyze the chemical reactions. This is why many vehicles have "catalyst warm-up" strategies that aim to bring the catalytic converter to its operating temperature quickly after starting the engine.

What causes a catalytic converter to malfunction?

Contaminants and build-up   
Over time, deposits of unburned fuel, oil, and other substances can clog the converter, obstructing the flow of exhaust gases. This build-up restricts the converter's ability to function effectively, resulting in decreased efficiency and increased emissions.  
Solution – regular maintenance, including engine tune-ups and using high-quality fuel and oil, can help prevent excessive build-up. Additionally, using a fuel additive designed to clean the catalytic converter can help keep it clear of contaminants.
Engine misfires and poor performance
Engine misfires, which occur when the air-fuel mixture in the engine's cylinders doesn't ignite properly, can lead to unburned fuel entering the catalytic converter. This unburned fuel can cause the converter to overheat and ultimately degrade its efficiency.  
Solution – address any engine misfires promptly by diagnosing your vehicle. Regular maintenance can help catch faults early on and pinpoint the exact issue causes. This is especially helpful when the check engine light can mask different faults.
Oxygen sensor failures
Catalytic converters rely on oxygen sensors to monitor exhaust gas oxygen levels and adjust the air-fuel mixture accordingly. A malfunctioning oxygen sensor can lead to an improper air-fuel ratio, causing the catalytic converter to work inefficiently or fail prematurely.  
Solution – regularly inspect and replace oxygen sensors according to the manufacturer's recommendations. This will ensure that the converter receives accurate data for optimal performance. 
Fuel and oil additives  
Certain additives present in some low-quality fuels or engine oil can contribute to catalytic converter malfunction by causing excessive deposits and contamination.  
Solution – use high-quality fuel and oil that meet the manufacturer's specifications. Avoid using additives that claim to enhance performance, they might contain substances harmful to the converter.  
Good practice in trying to prevent any malfunction is to use a diagnostics device, like OBDeleven NextGen, to stay on top of any unpleasant repair surprises. While not all of us may be mechanics and experts, diagnostics tools can help track any ongoing faults.
Get user-friendly diagnostic tool


Summing up  

Understanding the causes of catalytic converter malfunctions can save more than just money and time. Implementing preventive measures can extend its lifespan and ensure your vehicle runs efficiently. Regular maintenance, cautious driving, and addressing engine issues promptly are key to keeping your catalytic converter in optimal working condition, allowing you to enjoy a greener and smoother driving experience.
Disclaimer: Advice, how-to guides, and car care tips on our blog are intended as helpful resources for general maintenance and repairs. While we strive for accuracy, the information is provided to the best of our knowledge and should be used at your own discretion and risk.

Always refer to your vehicle's owner's manual or consult a certified mechanic for specific repair details and safety procedures.