What Does a Bad Catalytic Converter Sound Like?

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Okay, you understand that a bad or broken catalytic converter would make some kind of noise, but what type of noise does it make? What does a bad catalytic converter sound like?

Obviously, a bad converter makes rattling noises as you drive. However, a bad converter doesn’t only make noise, there are other signs it shows, too.

This article clearly explains the symptoms of a bad cat converter and how it would sound. It is important to quickly say that a bad catalytic converter can cause fatal internal engine damage. Hence, it is advisable to fix your “Cat” as soon as possible once it starts showing signs of failure.

What Does a Bad Catalytic Converter Sound Like?

Mainly, a bad catalytic converter makes a rattling noise as you drive. In some cases, if the converter fell off the exhaust pipe, you’d hear it scratch on the pavement as you drive. The rattling you hear is coming from the scattered honeycomb meshes inside the bad converter.

A cat converter is said to be “clogged” when its honeycomb meshes are blocked. If the clog is not removed, over time, it weakens the honeycomb meshes and causes them to break apart. Now, this explanation is why a bad converter is liable to make a rattling noise.

Related Post: Can a Clogged Catalytic Converter Cause Rough Idle?

How to Spot a Failing Catalytic Converter

What Does a Bad Catalytic Converter Sound Like

As hinted above, a bad catalytic converter doesn’t only make a rattling noise. There are other signs and symptoms you will notice.

1. Poor Engine Performance

This is practically the first sign of a bad or failing catalytic converter. The function of the “Cat” is to create a passage for harmful gasses from the engine to move away through the exhaust pipe.

So, when it cannot perform this function, the harmful emissions (which were supposed to be removed) may get back into the engine, and that’s what causes the significant drop in your engine’s performance.

2. Increase In Fuel Usage

Let’s say, your full tank lasts for complete 3 days, and suddenly, it’s no longer lasting that long, yet you can’t detect any improvement in your engine’s performance. So, what’s taking “more” fuel? Well, a bad catalytic converter can do this, and here’s how.

When the converter is clogged, it blocks exhaust fumes from going out; these fumes get back inside the engine and put the engine into high pressure. In a bid to keep running smoothly – even though there’s soot all over the engine’s internal components – your car would use more fuel.

How To Fix A Bad Catalytic Converter

It is best to drive into a mechanic workshop for cat converter replacement or fixing. The catalytic converter is the most important component of the emissions system; hence, it should be treated with carefulness.


Depending on the car model, the check engine light may illuminate when the catalytic converter goes bad.

More so, there are many things that could cause you to hear noises when driving, but when it’s a “rattling noise,” your catalytic converter needs to be checked. Furthermore, cat converter replacement is quite affordable.

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