Symptoms of a bad catalytic converter: Facts you should be aware of

Symptoms of a bad catalytic converter

In the modern age, we can’t think of any vehicle without a Catalytic Converter. It plays the most vital role in the car! The catalytic converter works using “catalyst” to create a chemical reaction in which the unburned fuel, CO and other harmful things are converted to pollution-free gases.

Nowadays almost every city is very strict about air pollution. So, every car user should be aware of symptoms of a bad catalytic converter and what to do to make it long-lasting also how to eliminate the failure.

Okay, don’t worry. We will discuss details so that you can understand easily the main symptoms of a bad catalytic converter and how to prevent it. So, let’s start!


The catalytic converter is located in between the Engine and Exhaust muffle. Now, the automotive makers introduce a very high-quality exhaust system for every vehicle. It often lasts 10 years or more. If your vehicle face no accidents and you maintain the proper maintenance guidelines like changing engine oil and filtering from time to time, cleaning or changing the air cleaner in due time, your car’s catalytic converter will get more durable. Always keep that in mind that “Driving with a bad catalytic converter is highly restricted.”

If you feel some unusual and uncommon behavior of the catalytic converter, you must have it checked by an automotive mechanic as soon as possible. As we are automotive mechanics, in the long run, we have discussed some common issues which indicate something is wrong with the Catalytic Converter.

  • Engine Check Light Comes on
  • Your Gas Consumption becomes abnormal
  • Engine Produces Excessive Black Smoke
  • Poor Pickup when you press the accelerator pedal
  • Engine Knocking
  • Engine Takes Long crank to start or Refuses to start
  • Bad Exhaust Smell and smoke
  • Excessive Heat under the Vehicle

# Engine Check Light Comes on

You may ask, how to tell catalytic converter is bad. The answer is pretty simple. If you see the dashboard of your car exhaust System Check- Light is showing orange color while the Engine is running, you’ll get to know that either your vehicle Exhaust system or Catalytic converter has issues.

Those Vehicles which have no Exhaust Check- light, only indicates engine check light. The catalytic converter fall code is P0420 that means catalytic converter is not operating. So, you need to replace your catalytic converter. Sometimes, the faulty oxygen sensor makes the check light to pop up. You have to make sure what the actual problem is with the help of an experienced mechanic.

#Your Gas Consumption becomes abnormal

You may notice improper exhaust gas passing through the Exhaust pipe due to the clogged catalytic converter. As a result, the engine cannot take proper air and the air-fuel ratio becomes imbalanced. Low fuel efficiency is one of the vital issues of catalytic converters.

#Engine Produces Excessive Black Smoke

As we know the root cause of black smoke is fuel not burning properly. There are so many parts that can cause this issue. Such as air cleaner, fuel injectors, turbocharger, and catalytic converter. If lots of carbon deposits on the catalytic converter, it becomes clogged.

#Poor Pickup when you press the accelerator pedal

Poor Pickup issue is one of the common problems of vehicles. If you don’t take care of your car, it can happen frequently. That’s why you need to clean or replace the air filter and fuel filter in due time. Change the Engine oil from time to time. Sometimes, your vehicle does not run as much as you accelerate the gas pedal. A clogged catalytic converter can make this.

#Engine Knocking

Problematic catalytic converter causes Engine knocking. Because of the improper air-fuel ratio, it cannot produce enough power of the engine. So, you have to confirm what the main problem is. It also can be other issues too.

#Engine Takes Long crank to start or Refuses to start

If you feel such types of symptoms, it can be a catalytic converter or other issues. If you can’t find out the actual problem you need to get some help from a good mechanic or a nearby garage.

#Excessive Heat under the Vehicle

When you feel Excess heat under the vehicle, it means your exhaust system is overheated. The main reason for an overheated Catalytic is unburned gas in the cat which actually burns inside it.

Besides, the failure of the O2 sensor and problematic Spark plug can cause this issue. So, Experts can easily understand what the actual fault is.

Symptoms of a bad catalytic converter


Well, we already have discussed the symptoms of a bad catalytic converter. Now, let’s discuss what causes the catalytic converter failure. Your catalytic converter can get clogged by unusual things that can’t pass through the catalytic converter. Here are some reasons, which can make your catalytic converter clogged.

  • Poor quality of gas
  • Excessive blow-by through the engine
  • Clogged Air Cleaner
  • Blown Head Gasket

Contamination of fuel with other liquid which cannot help getting out the rear exhaust pipe and it deposits in the catalytic converter. It can destroy the catalytic. Engine Coolant and Motor Oil Both Fluid Can Clog the Catalytic too! Both fluids are not allowed for passing through the catalytic.


If you have already addressed the symptoms of your catalytic, you should not drive the car. If you do the driving, it will be illegal. Also, you will be punished by the traffic police for polluting the environment. So, our suggestion is not to drive your car until you fix the issue.

It would be better if you bring the vehicle to your nearby garage or get a mechanic for solving the issue. If the mechanic advises you to replace your cat, do it immediately. Sometimes, it can be solved by cleaning with a catalytic converter cleaner. (amazon link )

How to Tell if You Need a New Catalytic Converter in Your Car (YouTube Video)

Final Words:

We hope now you are clear about the Symptoms of a bad catalytic converter. You must solve the problems of the catalytic converter at the primary stage. Or else, you’ll suffer because it’ll cause harm to other components of your vehicle.

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