Signs Of Catalytic Converter Failure

A catalytic converter is a part of your vehicle's exhaust system and it follows basic principles of chemistry to reduce the harmful emissions present in the gases emitted by the engine. Car engines run on petrol or diesel and when this fuel is burnt inside the engine, it releases harmful gases like carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). The function of a catalytic converter is to convert these toxic emissions into less harmful gases like carbon dioxide, water vapor, and nitrogen. The catalytic converter is located on the underside of the car and between the exhaust manifold and the muffler. 

A catalytic converter features a ceramic honeycomb structure that has small passages. This structure features a coating of catalyst material, which reacts with the exhaust gases to change their chemical structure. These catalysts are usually palladium, rhodium, and platinum. When the exhaust gasses pass through the exhaust manifold and into the catalytic converter, they go through the honeycomb structure and react with the catalysts. Here, two reactions take place: reduction and oxidation. The oxidation reaction converts the unburnt hydrocarbons and carbon monoxide into carbon dioxide and water vapor, whereas the reduction reaction reduces the nitrogen oxides into nitrogen and oxygen. 



There are primarily two types of catalytic converters: two-way and three-way catalytic converters. A two-way catalytic converter treats only carbon monoxide and unburnt hydrocarbons, whereas a three-way catalytic converter treats all three emissions, including nitrogen oxides.

Apart from the technical working of catalytic converters and their environmental benefits, we should also consider how important they are to the overall performance of the vehicle. If your catalytic converter is damaged and you choose to refuse to get it replaced, it can have a negative effect on how your car performs. In the early stage of damage, the converter does not affect your car's engine immediately. However, the longer it is left without being replaced, the engine performance can severely deteriorate. While catalytic converters typically last around 8 years or between 100,000 and 150,000 miles), they may be replaced sooner if you notice some of the symptoms mentioned below.

Over time, the catalytic converters can get clogged due to contaminations and soot buildup inside the ceramic passages. The ceramic honeycomb structure also deteriorates with time and can break into pieces due to age and occasional impacts from road objects. All these factors can choke the converter, disrupting the normal flow of exhaust gases. This directly affects the engine's performance to the point where you might face problems with the engine performance. Some other problems associated with clogged or old catalytic converters are poor acceleration, lack of power, engine hesitation, misfiring, and decreased fuel economy.

The Electronic Control Unit (ECU) in your vehicle constantly monitors the working of various sensors and components. If a catalytic converter has gone bad, a check engine light usually illuminates on the dashboard. Modern vehicles are today equipped with two oxygen sensors (upstream and downstream) that help to monitor the catalytic converter's efficiency as well. These two oxygen sensors compare the oxygen content in the exhaust gases entering and leaving the catalytic converter. If these sensors receive the same reading, it indicates an inefficient converter and allows the ECU to throw up a trouble code and “check engine light” on the dashboard. However, it's easy to check and diagnose your catalytic converter by retrieving the trouble codes using a diagnostic scan tool. The common catalytic converter fault codes are P0420 and P0430. You may also want to diagnose the oxygen sensors to be sure of the underlying cause. 

The last thing you want is for your vehicle to fail an emissions test. The Environment and Climate Change Canada (ECCC) regulates the emission standards for internal combustion engines for on-road and off-road vehicles. These emission standards work in harmony with the US Environment Protection Agency (EPA) federal standards. If your vehicle is emitting excessive exhaust due to a failed catalytic converter or your emission control equipment has been tampered with or removed, you might be subjected to warning, order, and/or fines. One of the most common reasons for a failed emission test is a bad catalytic converter, which should be replaced in such a scenario.

The catalytic converter is engineered to neutralize hydrogen sulfide emissions into hydrogen dioxide, which has no odor. A faulty or clogged catalytic converter will not be able to treat these emissions, releasing an intense sulfur gas from the rear of the exhaust. This leads to a stinky odor that smells like rotten eggs and is a sign of a catalytic converter failure.

If your vehicle is old and the service is overdue, the chances of wear on the catalytic converter increase. Excess burning of engine oil due to worn-out piston rings and bad valve guides can directly affect the catalytic converter. Bad spark plugs, worn ignition coils, and improper ignition timing can cause the air/fuel mixture to go unburnt into the exhaust. This unburnt fuel can ignite inside the catalytic converter, which is very hot and can lead to a meltdown of the ceramic catalyst. 

Other factors that contribute to the damage of catalytic converters are incorrect air/fuel mixture, bad engine tuning, malfunctioning oxygen sensor, and antifreeze leaking in the exhaust. These factors lead to increased soot and carbon deposits, causing the catalytic converter to become clogged, restricting the exhaust flow, and increasing the backpressure. Excess back pressure can lead to engine sputtering, stalling, and loss of power. Lastly, if you ‌take small trips in your car without going long distances, your catalytic converter may not get hot enough to burn the hydrocarbon deposits completely. To ensure it doesn't get clogged over time, take your vehicle out for an occasional long drive for 15 minutes or more. This will allow the converter to heat up sufficiently heat up and burn the deposit build-up.

To avoid damage and to make your catalytic converter last longer, follow your vehicle's recommended maintenance schedule. The best course of action you can take to fix your old and bad catalytic converter is to replace it with a new unit. Replacing your old and clogged catalytic converters will not only help you achieve better engine performance but will keep your car street legal and comply with the emissions standards. Failing to do so puts the complete exhaust system and its components at risk. Furthermore, purchasing the right catalytic converter is essential for a perfect fit and function. Therefore, you should consider the type of catalytic converter your vehicle uses or you can refer to our catalytic converter buying guide which will allow making an informed and better decision.