7 Symptoms & Signs of a Bad or Clogged Catalytic Converter

A catalytic converter is a critical component in every vehicle. It is designed to reduce the number of hazardous emissions discharged into the atmosphere.

Regarding the health effects of air pollution, we are well aware of the harmful impacts of combusted vehicle fuels on human health. Commonly hazardous substances include nitrogen dioxide, carbon monoxide, nitric oxide, and hydrocarbons. Instead of releasing these toxic byproducts, a catalytic converter uses chemical reactions to convert them into harmless elements such as carbon monoxide and water vapor before releasing them into the environment.

Here is everything you need to know about a bad or clogged catalytic converter, as well as the signs and symptoms to look out for!

catalytic converter

What you Need to Know

Admittedly, an engine’s combustion process is not perfect. In fact, it may produce bad reactions during the cycle. And due to the heat in the engine and the absence of a converter, it creates specific unwanted gases and annoying rattling noise.

One of the few examples is carbon monoxide (CO). When this poisonous gas is highly emitted into the atmosphere, it contributes to tropospheric ozone development. Then interacts with methane destruction in the stratosphere. It is harmful to the ozone layer. Because 78 percent of the air is boosted up and combines with oxygen in particular combinations, the heat of combustion also produces nitrogen dioxide (NO2). High amounts of nitrogen dioxide are likewise detrimental to the human body and the environment. Furthermore, unburned fuels or incomplete combustion creates hydrocarbons, which are also expelled through the tailpipe. Inhaling hydrocarbons is very hazardous to one’s health, especially if one has respiratory issues.

The good news is that catalytic converters are intended to reduce all three of these harmful pollutants. It is found underneath the car, just in the center of the exhaust system (between engine and muffler). It goes immediately behind the exhaust manifold before going to the resonator and muffler. It filters out pollutants before they go out of the stream tailpipe.

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Two Types

Eugene Houdry, a French chemical engineer, was the first to patent one in 1950.

Oxidation Reduction

There are two types of catalyst: reduction and oxidation catalyst. But, to recap what it accomplishes in chemical reactions, it is a compound that causes a chemical reaction to occur more quickly without being consumed. In other words, it is something that facilitates the reaction’s development.

Reduction and oxidation catalysts are made from a ceramic structure covered with a metal catalyst such as platinum, rhodium, or palladium. Making them likely to be a costly component of a vehicle. These metals are arranged in a honeycomb pattern. This arrangement exposes as much of the surface as possible while still using the least quantity.

The reduction catalyst, made up of platinum and rhodium, is the first stage. When a nitrogen oxide or nitrogen dioxide molecule comes into contact with the catalyst, a nitrogen bond is broken, forming a harmless diatomic gas (O2) molecule alongside the nitrogen molecule.

Oxidation is the next stage. It burns unburned hydrocarbons and carbon monoxide over a palladium or platinum catalyst, oxidizing them. And utilize the oxygen molecules in the exhaust and the oxygen freed up during the first stage (reduction stage). So there are 2 ways there: the first is to bond carbon monoxide to produce carbon dioxide, and the second is to oxidize unburned hydrocarbons as they pass through the catalyst.

Further, it uses oxygen sensors to monitor the level of oxygen in the exhaust system. These sensors are interconnected to an automated control system, which changes the air-to-fuel ratio by adjusting the carburetor. It lets the car’s fuel mix with more or less air before it enters the cylinders. As a result, it guarantees that there is just adequate oxygen in the exhaust to oxidize unburned hydrocarbons and carbon monoxide.

exhaust system of a car

What do they do?

Their primary job is to convert toxic nitrous oxides, carbon monoxides, and unburned fuel into less harmful nitrogen, carbon dioxide, and water. It is divided into two stages: reduction and oxidation.

When those hazardous components pass through the catalyst, they split up and develop into less toxic gases before exiting the pipe streamlines. In other words, when gas enters the system from the input (pipe linked to the engine), it is pushed over the catalyst, generating chemical reactions and breaking down pollutants. The less hazardous gases then go all the way to the output (which is linked to the car’s tailpipes) and finally out into the air.

Recent versions are engineered to be highly efficient. Indeed, premium models have manifested increased horsepower. According to reports, catalytic converters in most modern vehicles have reduced American emissions pollutants by an average of more than 70%. The bottom line is, it is without a doubt one of the most significant advances in automotive history.

7 Signs It’s Clogged

These components are critical in the conversion of harmful pollutants into safe gases. It is the safety defense against air pollution from automobiles positioned in a vehicle’s exhaust system (between the engine and muffler).

Even though they are designed to endure a long time, they can get contaminated, clogged, damaged, or overheat due to extended exposure to various contaminants as well as other factors. These issues will result in slow engine performance or, in the worst-case scenario, engine failure.

Here are some common signs of a clogged one:

1. Increased Emissions

Its function is to burn unburned fuel or gases that exit the engine, resulting in low carbon emissions. When your vehicle begins to emit increasing carbon emissions, it clearly indicates a clogged converter. It will then produce black smoke coming out of the exhaust resulting in a failed emission test.

2. Poor Performance

When carbon buildup inside becomes excessive, it causes a partial blockage within the catalytic converter. Alternatively, the internal system begins to melt due to the excess heat of unburned fuels, resulting in immense back pressures that reduces performance. Your car will shake regularly, and there will be backfires or unexpected bursts of pressure and engine stalling. It won’t go faster than 30-40mph.

3. Misfiring

Another thing, pay attention to is misfiring; if it happens, fix the problem as soon as possible. A misfire can quickly damage the component due to unburned gas exiting the combustion chamber and being discharged into the exhaust system.

picture underneath a car

The following factors may also cause misfiring:

  • Bad coils
  • Spark plugs
  • damaged/dirty fuel injectors
  • Busted head gasket
  • Other possible mechanical issues
  • Check engine light is on.

Oxygen sensors in modern cars analyze exhaust gas levels to monitor the effectiveness of the component. If the sensor detects that the gas has not been well converted, the check engine light will illuminate.

4. Bad Smell Coming Out from the Exhaust

Fuel contains a small number of sulfur particles that convert to hydrogen sulfide during combustion. The stinky sulfide is meant to be converted into odorless sulfur dioxide by a catalytic converter. It does not occur if the system is faulty or clogged. When a result, you will begin to smell like rotten eggs as some of the unburned gasses, including smelly hydrogen sulfide, escape your exhaust.

5. The Exhaust Produces a Rattling Noise

A rattling sound coming from your engine is because of components in the honeycomb-shaped chamber inside the catalyst breaking apart due to overheating or damage triggered by too much use of a rich fuel mixture. You’ll probably notice it when starting or switching off your car since the damaged pieces are rattling around inside.

6. Reduced Fuel Efficiency

The piston will be stressed if it is clogged. It is due to a system blockage that allows back pressure in the exhaust gas, resulting in reduced acceleration. You’ll then be forced to press harder on the gas pedal this way. It implies you’ll have to fill up your gas tank more frequently, which seems uneconomical, doesn’t it?

7. Hard Start and Overheating

When it is completely clogged, the engine cannot breathe because the exhaust gases have nowhere to go. It tends to travel back up into the engine, causing it to overheat and the head gasket to blow. Excess heat will overheat the cooling system, reducing its ability to cool the engine.

What Happens When it Fails?

Catalytic converters do go bad on cars, so what happens then?

  1. The converter blocked the exhaust system and increased the pressure way too much.
  2. Unburned fuel and other particles block the honeycombed mesh, causing pressure to build up.
  3. The temperature gauge will register somewhat higher because the exhaust gas remains in the engine for a very long period, causing it to overheat.
  4. The automobile will not go at a higher speed for much further, maybe not exceeding 30-40 mph.
  5. Overheating will become a significant problem.
  6. No start, hard start, and stalling are among the significant issues.

How do you Know if Yours is Going Bad?

A converter may sometimes survive ten years or more. Over time, it deteriorates and no longer converts the exhaust gases as effectively as it should. You will begin to notice several issues with the performance of your car. Here is the list

  1. Car fails in the emission tests
  2. The car pushes black smoke out
  3. The vehicle is juddering while accelerating
  4. Struggle going over 30-40 mph
  5. Emits sulfuric smell, or rotten eggs from the exhaust
  6. The car tends to overheat
  7. You’ll spend too much on fuel than before
  8. Check engine gauge indicator turns on
  9. Produced annoying rattling noise in the exhaust
  10. Misfiring
  11. Reduced performance/low power
  12. Going up a hill is difficult due to a lack of power
  13. Failing components; radiator, water pump gasket, cooling system hoses, etc. 

What does a Bad One Sound Like?

If it has come apart internally, it will produce a rattling sound. There is no distinct beat to the rattle noise. It may sound like rocks/pebbles bouncing around in the exhaust. It is because the honeycomb has disintegrated inside the pipe. When you open it, you will be startled by melted chunk-like fragments.

Can a Bad One Cause a p0300 Code?

If your car’s check engine light illuminates with the dreaded p0300 code, it means your engine is experiencing intermittent misfires. And, according to the p0300 code, at least two or more cylinders are encountering misfiring.

Random misfires happen for a variety of causes. The p0300 arbitrary misfire code is due to a faulty catalytic converter, which prevents the exhaust from breathing correctly, causing unburned gases to ignite within.

When p0300 develops, it must be repaired as soon as possible since it may cause further damage to your engine. P0300 occurs when worn-out spark plugs, torn spark plug wires, or a defective ignition coil.

P0300 Indications:

  1. Check engine light is on and flashing
  2. Lock of engine power
  3. Fuel smell coming out from the exhaust
  4. The engine runs rough and shakes.
  5. When you accelerate, you will experience jerking.

Can a Clogged One Cause a Misfire?

Fuel combustion supplies the energy to power the engine; therefore, effective fuel combustion is critical to engine functioning. A misfire happens when insufficient gasoline is burnt in a cylinder. And it could happen for many reasons. It could be a faulty ignition system, fuel system, or clogged exhaust system.

Typical Issues that Cause Misfires:

  1. Cracked plug
  2. Bad ignition coil
  3. Old fuel injector
  4. Weak fuel pump and fuel filter
  5. Dirty throttle body
  6. Bad airflow sensor
  7. Vacuum leak

Misfiring should not be taken for granted, especially if you often travel long distances. Ignoring the mistake might result in engine failure, catalytic converter damage, and risky driving conditions.

Unclogging it in 6 Easy Steps

A catalytic converter (cat-con) regulates the exhaust emissions of an internal combustion engine by catalyzing a chemical reaction. It contributes to reducing the environmental effect of cars.

A clogged cat-con, on the other hand, loses its capacity to filter out harmful gases. However, it is pretty expensive, so it is up to you if you want a new replacement or clean the existing one.

Step #1: You may get a cat-con cleaner in automotive supplies or browse online to find the best brand for your vehicle. Depending on the model of your car, you can follow the complete instructions provided. And if it doesn’t work, there is another way to unclog it, provided that you have little knowledge about automobiles.

Step #2: Remove the component . You will need a degreaser, a high-pressure power washer, and cleaning cloths. To lift the vehicle, you may additionally require a car jack and supports. Also, don’t forget to use safety equipment. And don’t forget to cool down the vehicle before you begin.

Step #3: The cat-con is located on the car’s underside, in the center of the exhaust system. Using a wrench, unscrew the bolts. Stubborn bolts may require oil to grease and soften. If it sounds like there are damaged components, shake the converter.

Step #4: Begin by cleaning the shell with a clean towel. Wash it with a power washer to get rid of the contaminants or debris out of the component. With moderate water pressure, clean the input and output pipes thoroughly.

Step #5: In a container, blend the degreaser and hot water. Soak it for approximately 1-2 hours. When finished, remove it from the mixture and rinse it with clean water. Allow it to dry before reassembling. Remember to reinstall it in the same manner that you removed it.

Step #6: Perform a quick test drive to ensure that everything is in place and working. Re-test the converter after test driving. If the result falls within the appropriate ranges, it indicates that the blockage has been cleared. If the unit fails too badly during testing, the only alternative is to replace it.

Keep in mind that they are a critical component for the proper performance of your car. Call a mechanic to do the job for you to guarantee proper unclogging. After all, hitting the road safely should be your top priority.

So rev up your engine with a safe and clean exhaust!

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