Can a bad catalytic converter cause the car to shut off? Explained!

(Last Updated On: July 4, 2023)

A car’s catalytic converter is a vital part of a vehicle that helps regulate the emissions from a car’s engine. But if your car is stalling, can a bad catalytic converter cause a car to shut off?

Usually, a bad catalytic converter should not be why a vehicle shuts off, as it is not a piece of the car’s ignition system. However, if a catalytic converter is extremely bad, it can affect the vehicle by causing it to shut off and refuse to start.

A broken or failing catalytic converter can have harmful effects on the smooth running of a car. Therefore it’s essential to understand what a catalytic converter does. You can then know the warning signs indicating a catalytic converter is old or worn out.

What Is A Catalytic Converter, And How Does It Function?

A catalytic converter is a component in a car’s exhaust system. It changes the toxic and lethal gasses a vehicle generates into less fatal gasses such as water vapor and carbon dioxide before releasing them through the exhaust into the atmosphere. The catalytic converter contains various valuable metals such as palladium, platinum, and rhodium arranged into a honeycomb, which the exhaust gases pass through.
The are other ways to remove hydrocarbons, such as a DPF filter and an EGR valve. Still, a catalytic converter alongside an EGR valve on a petrol engine is the perfect combination to meet emissions regulations. You can read more on the function of a catalytic converter here.

Can A Bad Catalytic Converter Cause The Car To Shut Off?

In typical scenarios, a bad catalytic converter shouldn’t be a reason for a car to shut off, as it is not a component of the car’s ignition system. However, a catalytic converter in extreme conditions can result in a car’s sudden shutdown or refusal to start.

A catalytic converter in terrible shape prevents the vehicle from operating correctly by restricting or increasing the amount of fuel through components called lambda sensors, which can affect the air intake of the cylinder. The increased back pressure from the exhaust and nowhere for exhaust gases to go but back into the engine means the car no longer receives oxygen which it can burn; starving the engine of oxygen could cause the cut to shut off. Remember, these are extreme circumstances, and you would already be aware of an issue with the car you continued to drive with.

In some cases, a car with a failing catalytic converter might start without any problem, but it might hamper you when it’s time to hit the accelerator. The engine could misfire under load (acceleration); you may not even be aware of this fault until it is time to drive. Driving with a misfire is a considerable risk as the car could go into limp mode, or the engine can shut down at any time. Engine shut-off might even happen when you’ve already hit the road. So, not to be caught off guard, if you notice a fault or something peculiar when you start the vehicle, be cautious before speeding off down the road.

broken catalytic converter internals

Signs Of A Failing Catalytic Converter

Certain signs indicate a faulty catalytic converter needs replacing.

  • Decrease In Engine Performance

First on the list and one of the most accessible signs to notice indicating that a car’s catalytic converter requires replacement is a reduction in the vehicle’s engine performance. Usually, this comes in the form of excessive fuel being pumped to the car engine, an increase in exhaust pressure, the engine light coming on, weak rates of acceleration, and reduced all-around top speed.

  • Reduction In Fuel Efficiency

A clogged catalytic converter can also severely reduce your vehicle’s overall fuel efficiency because your car engine cannot filter its emissions fast enough. And is not functioning in perfectly optimal conditions, which means that your car will consume more fuel to produce the same amount (or even less) of power. A weak acceleration can also lead to an increased amount of fuel consumed by your vehicle, giving rise to your need to purchase more fuel than usual. Suppose you happen to notice that you’re often going to the gas station regularly despite little or no alterations in your driving habits. In that case, your catalytic converter could be the issue. Endeavor to have it inspected as soon as possible. Because leaving this problem unattended can cause a dent in your pocket, as you will have to spend money constantly filling up.

  • Rattling Noises

Suppose you notice an unusual rattling sound coming from your car’s exhaust system, particularly when you turn on the ignition or while driving at high speed. In that case, it can only mean your catalytic converter internals may be damaged. Occasionally, it could just be a loose screw connecting the exhaust system or a broken hanger bracket, which could be an easy and economical fix. Worse, it could be a breakdown of the mesh in your catalytic converter due to age or a poor-quality aftermarket version. Therefore it needs to be replaced as soon as possible to aid in properly filtration of your car’s engine emissions.

  • Start-Up and Ignition Issues

With a severely clogged catalytic converter, emissions can pile up in the engine and choke out your car’s ignition system. This can cause a sudden shutdown of your car’s engine or refusal to ignite, which could prove dangerous, as your car could turn off while driving due to delayed removal of emissions by the catalytic converter. As such, seek repair immediately.

  • Constant Misfires

If your car is undergoing endless misfires while in motion, you should have a mechanic look at its catalytic converter. However, misfires aren’t caused by the car’s catalytic converter directly but by the supporting components. But bear in mind that they can damage the catalytic converter severely.

  • Unusual smells

A catalytic converter that has an unusual rotten egg smell has usually failed. Its job is to convert the tiny amount of sulfur in gas into an odorless gas. Sulfur smells eggy when burning, so if you can smell egg, the catalyst is not doing its job.

To summarise

The catalytic converter is not just important to the environment as it prevents the emission of lethal gasses into the air, it also ensures the smooth running of an automobile. Therefore it should be kept in reasonable condition as a bad catalytic converter can cause a car to shut off. So, if you discover an issue with yours, endeavour to fix it as soon as possible.

My name is Tom although my friends call me Tommy. Messing around with cars and bikes has always been a hobby of mine even from a young age. So I made it my day job 17 years ago. I am a fully qualified mechanic as you would expect. I've worked in all different areas of the motor trade, valeting, panel beating, engine repairs, I'm sure you get the idea. I enjoy sharing my wealth of knowledge and experience with others, which is the reason I spend a lot of time here writing for this website.

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