Can You Clean a Catalytic Converter? What Works

This article was updated in January 9, 2026 with new products and information by Mark S. Taylor

Seeing a check engine light is scary. It often means your catalytic converter is failing. A new part can cost over $1,500. A cleaning kit costs only about $20. Is it worth the risk to try and clean it? Yes, cleaning can work if you have carbon buildup. I have worked on many cars, and I have seen this work. But you must know when to clean and when to replace. This guide will show you what works. You will save time and money. Let’s look at the facts.

What Does a Catalytic Converter Do?

The converter cleans your exhaust. It takes harmful gases from the engine. It changes them into safe water vapor and gas. This helps the air stay clean. It uses special metals like platinum and palladium. These metals act like a filter. The part looks like a small box on your exhaust pipe. It usually lasts for ten years. It helps your car run clean.

Can a Catalytic Converter Be Cleaned?

It depends on what is wrong with it. You can clean light carbon deposits. These are like soot inside the pipe. Heavy buildup might come out with work. But a melted part cannot be fixed. If the insides are broken, do not clean it. Also, oil or coolant damage is permanent. Physical damage means you need a new one. Check the problem first.

Signs Your Catalytic Converter Needs Cleaning

Check Engine Light (P0420 or P0430 Codes)

The light comes on for many reasons. Codes P0420 and P0430 are specific. They mean the converter is not working well. The computer sees too much pollution. It means the part is “below threshold.” This means it is too dirty to work. You should scan the car to see this code.

Reduced Engine Performance

Your car will feel slow. You will lose acceleration power. The engine might hesitate. It feels sluggish when you push the gas. This happens because gas cannot get out. The back pressure hurts the engine. You need more RPMs to go fast.

Poor Fuel Economy

You will buy gas more often. A clog makes the engine work hard. It struggles to push exhaust out. This burns extra fuel. You will notice a drop in MPG. Check your miles per tank. If it drops, look for a clog.

Rattling Noise From Underneath

Hear a rattle when you drive? That is bad news. It means the inside is breaking apart. The substrate is loose. This is not cleanable. It is physical damage. You must replace the part. Do not try to fix a broken rattler.

Sulfur or Rotten Egg Smell

Do you smell rotten eggs? That is sulfur. The converter is not processing gas. It is failing to clean the fumes. This sign means the catalyst is dying. Sometimes cleaning helps. But often the smell means it is too late.

Failed Emissions Test

This is a clear sign of trouble. You fail if hydrocarbons are too high. The machine reads too much pollution. It is the most direct indicator. Your car is not safe for the road. You must fix it to pass.

Difficulty Starting

Does your car struggle to start? A severe clog can cause this. The engine cannot breathe. It is like holding your nose. This usually means the clog is very bad. It is an advanced stage of the problem.

When Cleaning Can Work vs When It Won’t

Good Candidates for Cleaning

Clean if the code is new. Look for early P0420 or P0430 codes. If the car runs okay, try it. A slow power decline is a good sign. No rattling noises is a must. Short trips cause carbon buildup. If you fix a misfire, clean the converter. Recent rich conditions are okay too.

Bad Candidates for Cleaning

Do not clean if you hear a loud rattle. A melted substrate is ruined. Oil or coolant contamination kills it. Road damage cannot be cleaned. An old car with high mileage should get a new part. If power is extremely low, just replace it.

Methods to Clean a Catalytic Converter

Method 1: Fuel Additive Cleaners (Easiest)

You pour a bottle into your gas tank. It is the easiest way to do it. Solvents in the liquid break down carbon. The deposits burn off as you drive. It cleans the whole exhaust system. It also cleans the oxygen sensors. This is safe for most cars.

Step-by-Step Process

1. Make sure your tank is low. Keep it at one-quarter full.
2. Pour the whole bottle of cleaner in.
3. Fill the tank with fuel.
4. Drive on the highway for twenty minutes.
5. Keep the speed steady. Do not let the car idle.
6. Use the whole tank before you judge the results.

Popular Products

• Cataclean: It costs about $25. It has strong solvents.
• Dura Lube: It costs $15. It cleans injectors too.
• Liqui Moly: It costs $20. It is a German brand.
• STP: It costs $10. It is a budget choice.

Pros and Cons

• Pros: It is very easy. You need no tools. It is cheap. It cleans the fuel system too. You do not remove parts.
• Cons: It only works on carbon. It will not fix broken parts. Results can vary. You might need two bottles. It is a temporary fix.

Success Rate

• Light buildup: It works 60-70% of the time.
• Moderate buildup: It works 30-40% of the time.
• Severe damage: It works less than 10% of the time.

Method 2: Physical Removal and Cleaning (Advanced)

You take the part off the car. This lets you clean it deeply. You can see the damage yourself. It removes hard chunks of carbon. You can also wash the sensors. This works better than additives.

Required Tools

• Jack and stands: You need to lift the car safely.
• Socket set: You need to turn bolts.
• Penetrating oil: Use WD-40 or PB Blaster.
• Pressure washer: Use a low setting only.
• Bucket and degreaser: You need a soap solution.
• Safety gear: Wear glasses and gloves.

Step-by-Step Process

1. Jack the car up high. Put it on jack stands.
2. Find the converter under the car.
3. Spray the bolts with oil. Wait fifteen minutes.
4. Unplug the oxygen sensors. Remember where they go.
5. Unbolt the converter from the pipes.
6. Take the converter off the car.
7. Look inside at the honeycomb part.
8. Wash the inside with a pressure washer. Use low power.
9. Soak it in degreaser overnight if it is dirty.
10. Rinse it and let it dry.
11. Put it back on with new gaskets.
12. Plug the sensors back in.
13. Clear the codes and take a test drive.

Warning About Physical Cleaning

Be very careful with the honeycomb. It is fragile. High pressure can break it. A weak part might break anyway. You need some skill to do this. Rusty bolts often snap. You must buy new gaskets.

Pros and Cons

• Pros: It is a thorough clean. You can inspect for damage. It removes loose debris.
• Cons: It takes a long time. You need tools. You might break bolts. You cannot fix a melted core.

Method 3: High-RPM “Italian Tune-Up” (Prevention/Light Cleaning)

Heat burns off carbon. This method uses high RPMs. The hot exhaust cleans the pipes. It pushes deposits out the back. It brings the part to the right heat. This is best for light dirt.

Process

1. Drive on the highway.
2. Get up to a safe speed.
3. Hold the RPM at 3,000 or 4,000.
4. Drive like this for thirty minutes.
5. Use a lower gear if you can. Do not speed.
6. Let the car cool down after.

Best For

Use this to stop problems. It helps with very light carbon. Do it for regular maintenance. It will not fix a bad clog. It keeps the system healthy.

Methods That DON’T Work (Myths to Avoid)

Dawn Dish Soap Soaking

No maker says to do this. It can hurt the metal coating. People on YouTube do it. But real experts say no. Do not soak it in dish soap.

Vinegar or Household Cleaners

These are too acidic. They can eat the substrate. They are not made for hot parts. The acid will corrode the insides. Avoid kitchen cleaners.

Lacquer Thinner

This chemical is very harsh. It might damage the catalyst. It is also a fire risk. It is not made for exhaust pipes. Do not use thinners.

Carburetor Cleaner (Spray)

Spray cleaner is too aggressive. It can ruin the honeycomb. The structure is very delicate. Only use specific cleaner liquids. Do not spray carb cleaner inside.

Hammer/Chisel “Gutting”

This is illegal in most places. You will fail emissions tests. The car will not pass inspection. It is not a repair. It is destruction. Do not gut the converter.

What Causes Catalytic Converters to Clog?

Carbon Deposit Buildup

Short trips are a main cause. The part never gets hot enough. Unburned fuel stays inside. It turns into carbon soot. This builds up over time. It restricts the flow.

Engine Problems Creating Rich Condition

Bad parts send too much gas. Faulty injectors leak fuel. Bad sensors mess up the mix. Extra fuel washes carbon in. It makes the “rich condition” worse.

Engine Misfires

A misfire means gas did not burn. This raw fuel goes into the exhaust. It gets very hot. It damages the converter. It creates lots of carbon.

Oil or Coolant Contamination

Leaks are very bad for converters. Head gaskets leak coolant. Worn rings burn oil. These fluids “poison” the metal. They coat the precious metals. This is usually not cleanable.

Old Age and Heat Cycles

Parts wear out over time. The car gets hot and cools down. This happens again and again. The substrate gets weak. The coating wears off. Old parts simply fail.

How Much Does Catalytic Converter Cleaning Cost?

DIY Cleaning Costs

• Fuel additive: $20 to $40.
• Tools: $50 to $150 if you need them.
• New gaskets: $20 to $50.
• Total DIY: $20 to $240.

Professional Cleaning Service

Most shops do not offer this. They prefer to replace parts. If you find one, it costs $150 to $300. They will likely tell you to buy a new one.

Replacement Costs (For Comparison)

• Aftermarket part: $200 to $800.
• OEM part: $800 to $2,500.
• Labor: $100 to $300.
• Total replacement: $400 to $3,000.

When Cleaning Is Worth Trying

Try it if the symptoms are mild. If you have a P0420 code, try it. If the car has less than 100,000 miles, try it. If you fixed an engine issue, try it. Spending $20 is better than $1,500.

How to Tell If Cleaning Worked

Immediate Signs (24-48 Hours)

The light might go off. The car will feel faster. The gas pedal responds better. Acceleration is smoother. You will feel a difference right away.

Long-Term Success (1-2 Weeks)

The light should stay off. The fuel economy goes up. Symptoms do not come back. You can pass an emissions test. This means it worked well.

When Cleaning Failed

If the light comes back fast, it failed. If you feel no power change, it failed. If the smell remains, it failed. If you still fail the test, replace the part.

How to Prevent Catalytic Converter Problems

Regular Maintenance

Fix the check engine light fast. Do not ignore it. Fix misfires right away. Replace O2 sensors on time. Use good quality fuel. Change your oil to stop burning. Read our guide on essential car maintenance for more tips.

Driving Habits

Drive on the highway sometimes. This burns off carbon. Try not to idle too much. Let the car warm up up. Do not run the tank to empty. This helps the fuel pump too.

Address Underlying Issues

Fix rich running problems. Repair vacuum leaks. Replace bad fuel injectors. Fix head gasket leaks quickly. Learn more about common engine problems to stay safe.

Preventive Treatments

Use a fuel additive sometimes. Do it three or four times a year. This is vital for short trips. Buy gas with detergents in it. This keeps the system clean.

Should You Clean or Replace Your Catalytic Converter?

Clean First If

You have a code but no bad symptoms. The car has low mileage. There is no rattling noise. You fixed a recent engine problem. You mostly drive short trips. You are on a budget.

Replace Immediately If

You hear a loud rattle. The power is very low. Cleaning failed twice. The car is over ten years old. You have oil or coolant leaks. You see physical damage. You have an inspection soon.

FAQ About Can You Clean a Catalytic Converter

How to clean a clogged catalytic converter?

You can use a fuel additive cleaner. You can also take it off and wash it. Driving on the highway helps too.

Does cleaning a catalytic converter really work?

Yes, it works for carbon buildup. It does not work for physical damage. It is worth a try for light clogs.

What are the signs of a clogged catalytic converter?

The main sign is a check engine light. The car will feel slow. You might smell rotten eggs. Fuel economy will drop.

What can you put in your gas tank to clean your catalytic converter?

You can put specialized cleaners in. Brands like Cataclean work well. Lacquer thinner is not safe.

Can you clean a catalytic converter without removing it?

Yes, you can use fuel additives. This cleans it while you drive. It is the easiest method to use.

The Bottom Line

You can clean a catalytic converter. But it depends on the damage. Fuel additives are great for carbon. They are cheap and easy. Physical damage cannot be fixed. You must replace a broken converter. Cleaning costs very little money. Replacement costs a lot. Try cleaning first if the car runs okay. If it fails, buy a new part. Prevent issues with good care. Drive on the highway to burn off dirt. Fix codes fast to save the part.

Quick Summary

• Cleaning works for carbon, not broken parts.
• Fuel additives are the cheapest and easiest method.
• Physical removal works better but takes more skill.
• Rattling noises mean the part is broken.
• Address engine issues to prevent future clogs.
• Try a $20 cleaner before a $1,000 replacement.
• Regular highway drives help keep the system clean.