Can a Bad Catalytic Converter Ruin Your Engine?

Can a Bad Catalytic Converter Ruin Your Engine

Can a bad catalytic converter ruin your engine? This is something that you begin to wonder if you see the symptoms that it is already failing. Many people do not know how badly dented or dislodged catalytic converters can affect a car.

Depending on the cause, a bad catalytic converter can cost thousands of dollars to replace. But before we go any further, let’s learn more about what a catalytic converter does, what might cause damage, and the symptoms that it’s already bad.

Signs and symptoms of a bad catalytic converter?

 The catalytic converter is a critical component of your vehicle’s emissions system. It cleans up harmful gases from the exhaust and helps reduce smog. 

The converter includes a honeycomb-shaped metal catalyst that contains precious metals like platinum and palladium, which are needed to break down pollutants effectively.

These metals can be damaged by high temperatures and chemical exposure. That’s why they need to be replaced before they fail entirely.

Here are some signs that indicate it could be time to replace your catalytic converter:

1. Check Engine Light – A bad catalytic converter can cause many problems, from reduced performance and poor fuel economy to reduced engine life. The first symptom of a bad catalytic converter is usually a check-engine light.

If your car’s computer (PCM) triggers a P0420 trouble code, it means it has detected a problem with the catalytic converter.

2. Poor throttle performance – A bad catalytic converter can also cause poor performance. If the car hesitates or feels sluggish when accelerating, it may indicate that you need new catalytic converters.

3. Poor fuel economy – You might also notice that your vehicle consumes more gas than usual. This is another sign that something is wrong with the catalytic converter in your car. You may want to address this issue immediately as we see surging gasoline prices in the U.S. in 2022.

4. Smell of sulfur – If you notice an unpleasant odor coming from your vehicle’s exhaust, this could be a sign that something is wrong with your catalytic converter.

5. Discolored Casing – Another symptom that may indicate a problem with your catalytic converter is discoloration on the device’s casing. This discoloration may appear as rust or other stains on the metal casing.

6. Starting Issues – A clogged catalytic converter may prevent the engine from getting enough air and fuel to start up. This is especially true if your car has an oxygen sensor problem or if you’re driving in icy weather conditions.

7. Increased Emissions – If your car has excessive emissions or doesn’t pass an emission test, this could be a sign of a bad catalytic converter.

8. Engine Misfires – A misfire means that one or more of your engine cylinders aren’t receiving enough fuel due to a problem with the ignition timing system or spark plugs; however, it can also be

9. Rattles or other noises – Rattles or other noises coming from the inside could mean that the catalyst or honeycomb had reached its lifespan and broken down into pieces. This would require you to replace the entire system with a new one instead of just replacing parts.

Now that you have already diagnosed that you have a bad catalytic converter, what should you do next?

Well, there are several options available to you. You can choose to replace it yourself or take it to a mechanic who will replace it at a nominal cost. Or you can choose not to fix it and continue driving with your old catalytic converter until it fails completely.

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Can a bad catalytic converter ruin your engine?

Yes, it can. But only if the honeycomb has already started to disintegrate. Catalytic converters are very close to the engine, so they can be damaged by heat and vibration.

Since modern engines use valve timing to recover exhaust gases, the broken pieces of the honeycomb could be ingested back into the combustion chamber. These broken pieces can damage your cylinder walls, which is a costly repair job.

In the past, there were models notorious for this: The Nissan QR25DE and Nissan VQ35DE are known for having problems with their catalytic converters failing prematurely due to vibration caused by drivetrain vibrations.

What happens if you don’t replace a bad catalytic converter?

But what will happen if you keep driving without replacing it? Aside from possible engine damage, the exhaust gases from your car will start polluting the environment and affecting other people around you.

Remember that the primary function of the catalytic converter is to change the harmful compounds from an engine’s emissions into safe gases, like steam.

A damaged catalytic converter will not just affect how much money you’re spending at the pump but also how well your vehicle runs.

Without oxygen in the mix, your engine will use more fuel than necessary and run less efficiently than usual. This means that not only will you be spending more on gas, but your engine won’t be getting as much power out of it as possible.

You may also experience the following:

  1. Your vehicle will not be able to pass an emissions test
  2. Your vehicle will produce excessive amounts of smog-causing emissions
  3. You will be subject to fines by your local government or by the California Air Resources Board

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Can you fix a catalytic converter without replacing it?

The answer is it depends. The main reason for damage to the catalytic converter is that the honeycomb material reaches its lifespan and is broken. If this happens, you will need to replace it with a new one. However, if the damage is only in the case or housing, it is still repairable.

The reason why the honeycomb material can’t be repaired is because of its internal structure. A honeycomb catalyst has many passages, separated by thin walls called cells.

These cells are made from ceramic materials and precious metals to withstand high temperatures when exposed to exhaust gases from a car engine.


In short: a bad catalytic converter is something that you would want to repair as soon as possible. Bad catalytic converters can certainly damage an engine. Suppose you’re not paying attention, and your honeycomb has started disintegrating. In that case, there’s a good chance that broken pieces could be ingested back into the combustion chamber.

Replacing your damaged catalytic converter is vital in avoiding further damage to your car. If you’re having trouble with your car’s emissions, start by having a mechanic check the converter.

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