10 Symptoms of a bad Catalytic Converter | How to Fix a bad Catalytic Converter?

The catalytic converter is the most important part of the vehicle. It helps to control the emission rate of exhaust gases. It is placed in the exhaust system between the muffler and the engine. It uses ceramic-coded beads and a variety of precious metals (catalysts) to transform pollutants such as nitrogen oxides and unburned gases into nontoxic gases. This article mainly explains the catalytic converter function, symptoms, and replacement cost.

What is a Catalytic Converter?

A catalytic converter is a mechanical unit that converts toxic gases and pollutants in exhaust gas from an IC engine into less-toxic pollutants by catalyzing a redox reaction.

Catalytic converters are usually used with internal combustion engines fueled by gasoline or diesel, including lean-burn engines, and sometimes on kerosene heaters and stoves.

Catalytic Converter

A catalytic converter is an important part of a vehicle’s emissions system. It is designed to extend the life of the vehicle but can fail if it becomes clog. It has a honeycomb structure.

The honeycomb structure is designed to allow contaminants to flow over more exposed surfaces, converting hydrocarbons, carbon monoxide, and nitrogen oxides into less hazardous elements like carbon dioxide. Platinum is a costly product, but it is often utilized as a catalytic converter.

Symptoms of Bad Catalytic Converter

As the catalytic converter goes bad, it gives one of the below-given symptoms:

  1. Check engine light illumination
  2. Poor acceleration
  3. High fuel consumption
  4. Smell of Sulfur
  5. Rattling noise
  6. Increased emissions
  7. Failed emission test
  8. Engine misfiring
  9. Black smoke from the exhaust pipe
  10. Stalling

Symptoms of Bad Catalytic Converter

1) Check Engine Light Illumination

The check engine light starts illuminating as the catalytic converter goes bad. This check engine light locates on the dashboard of the vehicle. The latest cars also have oxygen sensors. These sensors observe the efficiency of catalytic converters by inspecting the exhaust gas level.

As the oxygen sensor observes that the exhaust gas is not being properly catalyzed, it sends a signal to the “Check Engine Light,” and the engine light starts illuminating. This light may also illuminate due to many other reasons, such as engine overheating, low coolant level, etc.

One of the best methods to get the car trouble code is to use a diagnostic scan tool. P0430 and P0420 are two famous trouble codes that represent catalytic converter failure.

Read More: Causes of Check Engine Light Illumination

2) Poor Acceleration

The engine’s poor acceleration is one of the major symptoms of a blocked catalytic converter. In such a situation, the engine couldn’t produce power according to the vehicle’s requirements.

The catalytic carbon clogs due to the excessive carbon build-up in the honeycomb structure, or internal components begin to melt due to excessive heat from unburned fuel.

For efficient working of the engine, your engine exhaust flow must be good. As the converter goes bad, you will observe poor acceleration issues.

3) High Fuel Consumption

Improvement or deterioration in fuel economy is one of the signs of a bad catalytic converter. Better mileage sounds good enough, but it may badly damage the engine and lead to a costly repair.

In the case of a clogged exhaust system, the fuel doesn’t combust efficiently; due to that, engine efficiency reduces, and it needs to work harder to meet the power requirements. So, in general, a defective catalytic converter uses more fuel, but in some cases, it uses low.

4) Smell of Sulfur

The sulfur smell is one of the common signs of catalytic converter failure. As the converter blocks, it restricts the flow of exhaust gases, and the engine’s fuel-air mixture becomes rich (if there is too much fuel, the fuel does not burn).

Combustion of this excess air-fuel mixture can produce an odor similar to burning sulfur or rotten eggs.

5) Rattling Noise

When the parts of the catalytic converter become cracked due to engine overheating or damage, it may start producing a rattling noise coming from beneath the car. This noise usually becomes very high during the startup of the vehicle.

6) Increased Emissions

The main function of the catalytic converter is to expel harmful emissions. As the catalytic converter clogs or damages, it doesn’t perform its job efficiently, and the exhaust gas emission rate increases. This leads to increased engine emissions in the vehicle.

In case of a bad converter, your vehicle may also expel black exhaust smoke from the tailpipe when accelerating it.

7) Failed Emission Test

A failed emission test is also a sign of a bad catalytic converter.

8) Engine Misfiring

When the catalytic converters become clogged, the oxygen flow into the engine becomes restricted, and the engine requires large amounts of oxygen for efficient combustion of the fuel. In such conditions, a large amount of unburnt gases are collected that can cause engine overheating and can also cause the engine to stall.

When your engine starts misfiring, you must repair it immediately because it may lead to a costly repair.

Read More: Symptoms and causes of Engine Misfire

9) Black Smoke from the Exhaust Pipe

When the catalytic converter fails, gases start building up in the exhaust. As they build up, the gasses become thicker and have a darker color. Therefore, thick and dark-colored gases coming from the tailpipe are a symptom of a damaged catalytic converter.

10) Stalling

The engine can burn too much fuel if the catalytic converter is clogged. It also creates back pressure, making it difficult for the engine to escape exhaust gases.

If the car stalls 2-3 seconds after starting, it may be due to a clogged converter. This is because it can take a few seconds for the pressure in the exhaust system to build up before the engine stalls and shuts down.

Causes of a bad Catalytic Converter

  1. Improper fuel mixture
  2. Incorrect timing
  3. Bad spark plugs
  4. Bad oxygen sensor
  5. Sticking float
  6. Defective fuel injector
  7. Faulty check valve.

1) Poor Engine Maintenance

Engines need to be serviced from time to time. Old and poorly maintained engine burns oil due to worn-out valve guides, struck rings, and worn cylinder walls.

This burning oil produces products that can damage the converter. Incorrect timing and incorrect fuel and air mixture also lead to a catalytic converter failure. These factors damage not only the converter but also other engine parts.

2) Bad Oxygen Sensor

A malfunctioning oxygen sensor sends the wrong readings of the exhaust gases to the car’s computer. These readings lead to improper fuel and air mixture.

When the mixture is too rich, unburned fuel gets in the converter. Too lean mixture prevents the converter from converting hydrocarbons to safe elements, making the vehicle fail an emissions test.

3) Short Trips

If you only use the car for short trips, the catalytic converter does not get hot enough to burn hydrocarbons completely. This would cause clogging of the catalytic converter after some time. You can prevent this by driving your vehicle for longer to allow the converter to heat up sufficiently and burn the deposit build-up completely.

4) Bad Spark Plug Wires or Spark Plugs

Another cause of a bad catalytic converter is failed spark plugs or spark plug wires. When the plugs misfire or fail to fire, they force unburned duel to get in the exhaust system. The unburned fuel ignites, causing a complete or partial meltdown of the honeycomb structure.

5) Coolant Leaks

Coolant or antifreeze leaks in the combustion chamber can lead to serious problems. A blown head gasket mainly causes these leaks. When the leaks get to the exhaust system, they clog the catalytic converter preventing it from working effectively.

6) Unburned Fuel

Excess heat is a major cause of issues in the internal vehicle parts. The engine exhaust is always hot. When contaminants like unburned fuel leak into the exhaust system, they burn up, thus causing the honeycomb structure to melt.

The honeycomb helps the catalytic converter to perform. A damaged or melted honeycomb blocks and restricts exhaust flow. This is what causes the engine to start misfiring and having a rattling noise.

Catalytic Converter Location

The catalytic converter is located between your muffler and the exhaust pipe manifold on the exhaust pipe system.

Depending on the car engine, the distance where it’s installed from the engine could differ a lot. On some engines, the catalytic converter is installed directly on the exhaust manifold, while on others, it could be installed almost in the middle of the exhaust pipe.

How to fix a bad Catalytic Converter?

1) Fuel Additives

One easy way of fixing a clogged catalytic converter is using fuel additives. The fuel additives help the engine run more cleanly and help clean catalytic converter deposits. For instance, if you run a vehicle with low octane fuel, you can fix the converter by changing it to high octane fuel.

2) Italian Tune-Up

The Italian tune-up method is used to fix quite a number of issues in a vehicle, and a bad catalytic converter is one of them. All you are required to do is to push your vehicle harder to hear the catalytic converter enough. The converter should be heated to a high temperature of between 426 °C (426°F) and 1,000 °C (1832°F).

Run the vehicle a little longer than usual, and this will help burn off any carbon deposits in the catalytic converter, oxygen sensors, cylinder head, and intake valve. This, however, may not work if the converter is extremely clogged.

3) Fix Exhaust Problems

Exhaust leaks are common and can skew oxygen sensor readings without setting other DTCs. A careful search might reveal exhaust leaks that, when repaired, “restore” catalytic converter function, at least from the point of view of the ECM.

Worn exhaust gaskets and corroded flex pipes are two common issues that are significantly less expensive and more effective than replacing a catalytic converter.

4) Cleaning the Converter

Removing and cleaning the catalytic converter is another potential fix. After removing the catalytic converter, use a pressure washer to blast out any contaminants from the matrix. Be sure to flush the unit from both ends.

Another way to clean the catalytic converter is to soak it overnight in a combination of hot water and degreaser or laundry detergent. This process takes longer but is necessary to dissolve the deposits clogging up your catalytic converter.

After washing or soaking, be sure to dry the catalytic converter completely before reinstalling.

Catalytic Converter Replacement Cost

The replacement or repair cost of the catalytic converter varies according to the vehicle model, your living area, and the labor cost. The average replacement cost of the catalytic converter is between $940 and $2470, including parts and labor. The catalytic converter cost itself can be up to $2260 of that. That might be close to your car’s value or more!

FAQ Section

What is the average life of a catalytic converter?

The average lifespan of a catalytic converter is roughly 10 years or 100,000 miles. However, many factors can affect the lifespan of a catalytic converter, such as the quality of the converter, the type of vehicle it’s in, and how well the vehicle is maintained. Many catalytic converters will last the life of the car, while others have a scheduled service for when the catalytic converter is to be replaced.

What is the Catalytic Converter function?

A catalytic converter is a unit that fits into the front part of the exhaust system of a vehicle, close to the engine, to reduce the emission of gaseous pollutants, such as carbon monoxide (CO), nitrogen oxides (NOx), and hydrocarbons (HCs).

What happens when the catalytic converter goes bad?

The main function of the catalytic converter is to clean emissions from the vehicle and prevent air pollution. A bad catalytic converter causes the check engine light to illuminate, the engine to misfire, and the vehicle may fail to start. Other signs are dark exhaust smoke, the smell of sulfur from the exhaust, and reduced acceleration.

What does a bad catalytic converter sound like?

If you can hear a rattling noise coming from the catalytic converter, it can mean it’s bad. However, unfortunately, there isn’t necessarily one specific sound from the exhaust that indicates a problem with the catalytic converter.

Can I drive with a bad catalytic converter?

Most of the problems related to catalytic converters do not affect the function of your vehicle. Avoid driving your car if you have to deal with a fully plugged catalytic. The bad catalytic converters will give off higher emissions than allowed by the state. So, a car with a malfunctioning catalytic converter will not pass a vehicle inspection.

Can a bad catalytic converter ruin your engine?

Yes, it can, but it is more likely that your engine will just shut off and not run until you fix the damaged catalytic converter. A clogged or damaged catalytic can create high backpressure into the engine, damaging other parts of your car’s engine or emission system, which could lead to severe engine failure.

Can a catalytic converter unclog itself?

Generally, a clogged cat cannot unclog itself. The only way a cat converter can sometimes unclog itself is via driving long at a particular level of high RPMs. Since you have to sustain it for a very long, it will be nearly impossible to happen without any effort on your part.

What are the 3 most leading failures of a catalytic converter?

Most catalytic converter failures fall under one of three categories: broken, melted, or overheated converters.

Can a car run without a catalytic converter?

As part of a car’s exhaust system, the catalytic converter helps to reduce air pollution. You will not harm your engine or car in any way by driving without a catalytic converter, but it will increase exhaust gas emissions.

Can you clean a catalytic converter instead of replacing it?

Cleaning a catalytic converter is not recommended by any vehicle manufacturer. It can damage the internal catalyst and render this mandated system useless. The best solution is to have a professional mechanic replace the catalytic converter.

What are the signs of a faulty catalytic converter?

  1. Check engine light illumination
  2. Stalling
  3. Black smoke from the exhaust pipe
  4. Poor acceleration
  5. Engine misfiring
  6. High fuel consumption
  7. Failed emission test
  8. Smell of Sulfur
  9. Increased emissions
  10. Rattling noise

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