Bad Catalytic Converter Symptoms: Breaking Down The 8 Issues

It’s important to know about the bad catalytic converter symptoms so that you can spot them immediately and take the vehicle to a servicing shop for maintenance.

What Are Bad Catalytic Converter Symptoms?

The catalytic converter is a key component of the exhaust system of a car: It changes some properties of the harmful gasses which are produced when running the engine. As a result, the emitted gasses make a less damaging impact on the environment. 

A broken catalytic converter is not uncommon at all. Any external impact such as debris on the road or overheating of the engine’s internal components can affect it. Let’s learn about some catalytic converter symptoms with Car From Japan.

1. Engine Misfiring

The catalytic converter can overheat and show signs of failing when the engine misfires. And it is the first symptom of a bad catalytic converter. An extremely rich fuel mixture causes ignition by making raw fuel enter the converter. The condition is dangerous since it can melt the catalyst components.

bad catalytic converter symptoms
The catalytic converter can overheat and show signs of failing when the engine misfires. (Source: Spidersweb)

2. Loss of Power When Accelerating

Losing power during acceleration or going uphill is one of the most common clogged catalytic converter symptoms. Mechanics often misdiagnose this cause, especially in case of partial clogging, and suggest changing of a few components, which is unnecessary.

effects of a bad catalytic converter
Losing power during acceleration or going uphill is one of the most common clogged catalytic converter symptoms. (Source: TVP infor)

You can be sure about this problem by applying a simple test. Apart from the obvious low-powered acceleration, you can check the exhaust with your hand.

Ask an assistant to hold the car’s rpm at between 1800 and 2000 while you will check the exhaust push with your hand from behind the tailpipe. If you get a hot feeling of exhaust flow, the converter is definitely clogged.

3. Degraded Performance

An overall degradation in the engine performance is another sign. It happens because of the back pressure that the failing converter creates, affecting the engine and preventing it from running freely. It makes your car shake and the sudden burst of pressure can sometimes stall the engine too while you are driving.

4. Reduced Exhaust System Performance

Another way to notice bad catalytic converter symptoms is to keep an eye on the exhaust system’s performance. It will degrade if the converter is failing and the problem can be traced back to an error in the fuel system.

driving with a bad catalytic converter
Keep an eye on the exhaust system’s performance to know if your catalytic converter is okay or not. (Source:Car Throttle)

5. Fuel Vapor

If your vehicle has a carburetor instead of a fuel injection, you can be sure of a poor catalytic converter by doing the fuel vapor test. Remove the air cleaner and ask an assistant to flash a torchlight near the carburetor intake.

Rev the engine and see if there’s a cloud of vaporized fuel over the carburetor. If this is the case, you can assume without a trace of doubt that your car’s catalytic converter has a clog.

6. Increased Emissions

Increasing emissions is one of the symptoms of a bad catalytic converter you should notice. When a converter is failing, it can’t do its job properly, which is to reduce gaseous emission. 

So, a high level of carbon emission is the obvious consequence of a bad exhaust system. The effects of a catalytic converter are the damage of the entire exhaust system if you don’t fix it quickly.

can i drive with a bad catalytic converter
A high level of carbon emission is the obvious consequence of a bad exhaust system. (Credit: Getty Images)

7. Stolen Catalytic Converter

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.

8. Catalytic Converter Need Regular Maintained

Further small bad catalytic converter symptoms are reduced acceleration, sluggish engine performance, excessive heat under the vehicle, dark exhaust smoke, and the smell of sulfur or rotten eggs from the exhaust. 

Some of those symptoms can also result from other defective parts of the emissions system, so it’s important to get a mechanic diagnosed when it’s time to replace your catalytic converter. 

Keeping your exhaust, emissions, and combustion systems in good shape will minimize the risk of your catalytic converter failing before its due to breaking down – often 10 years or more.

catalytic converter symptoms
Catalytic converter needs to be maintain frequently. (Source: BanksPhotos)

Driving With A Bad Catalytic Converter: Yes or No

If your beloved car is showing catalytic converter problems, you may wonder ‘can I drive a car with a bad catalytic converter’ or ‘how long can I drive with bad catalytic converter’. Here is the answer for you.

A Bad Catalytic Converter Can Be Driven Indefinitely

Driving with catalytic converter failure symptoms is not too dangerous and you can still drive your car as usual. However, you will see there is a drop in the performance of the catalytic converter. 

In case the catalytic converter is plugged, it will prevent you from running your vehicle. In some situations, the catalytic converter might come to be completely fused directly or over time, then you need to replace it immediately.

A car with these failing symptoms can be driven indefinitely and doesn’t hurt much depending upon your drive and the severity of your issue. 

If your catalytic converter is slightly bad and the only destinations you ride to are close by, it is probably not a disaster for you, and you don’t need to rush and get it replaced or get it unclogged.

A Bad Catalytic Converter Can Burn Through Overtime

The inner fiber of your catalytic converter may be burned through if the car engine is running or burning oil too much. It doesn’t matter if you still drive your car as far as you want, but you will observe a smell and some smoke.

What To Do If You Think You Have a Faulty Catalytic Converter?

Unfortunately, you cannot repair a faulty catalytic converter. Replace it sooner rather than later to avoid contributing to air pollution, and to avoid potential collateral damage to your engine and exhaust system.

You can replace it at a trustworthy mechanic or garage. They are the best places to do so.

Want to learn how to tell if you need a new catalytic converter in your car? Check out this video of Scotty Kilmer.

How Do You Unclog a Catalytic Converter?

There is an array of products and methods that claim to unclog a clogged-up catalytic converter. And while some of these approaches may work, many of them will not. The only foolproof way to address the problem of a clogged catalytic converter is to replace it with a new one.

How Much Does It Cost To Replace A Bad Catalytic Converter

Replacing a catalytic converter isn’t cheap. By one estimate, most replacements will cost between $1,300 and $1,600. Exactly how much the job costs will depend on many factors, including the type of vehicle you have.

clogged catalytic converter symptoms
Replacing a catalytic converter isn’t cheap. (Source: Katalizatori)

Should you decide to tackle the job yourself, expect to pay anywhere from approximately $100 to over $1,000 for a replacement catalytic converter. Once again, exactly how much the part may cost will depend on many factors, including the type of vehicle you have.

Sometimes, you’ll find universal catalytic converters that are relatively inexpensive. The problem is, typically, those components have to be welded or clamped into place, and that makes replacement a lot more difficult.

A better option? Be diligent about preventive maintenance. Keep your exhaust system clean and well-maintained so you can avoid catalytic converter problems in the first place.


Most bad catalytic converter symptoms do not affect the function of your vehicle. But if you have to face a fully plugged catalytic, keep driving your car is the thing you have to avoid.

In some countries, it is illegal to drive a car with a damaged catalytic converter since smog from your car will cause many bad impacts on the environment. Thus, getting your car a new catalytic converter is what you need to do in this case.