How to Unclog a Catalytic Converter? All That You Need To Know

You are reading this because you are looking for information on how to unclog a catalytic converter. Of probably a truth, once you drive a car with an internal combustion engine, you should expect to experience a clogged catalytic converter. Why is that?

Well, catalytic converters essentially convert dangerous exhaust emissions into “safer” gases. Since a lot of smoke passes through the exhaust, it’s only a matter of time before it becomes clogged.

What you are about to read will show you how to keep your catalytic convert functioning optimally. Read on!

What Are the Symptoms of a Clogged Catalytic Converter?

Driving a car with a clogged catalytic converter can be a pain in the butt. Besides the environmental pollution issues, you run the risk of damaging your car’s engine. Thankfully, some symptoms pop up when a car has a clogged catalytic converter. Here they are:

How to Unclog a Catalytic Converter

Engine Performance Issues

One of the issues with a clogged catalytic converter is exhaust backpressure. This means that the exhaust gases are trapped within the car. Internal combustion engines need the right air-fuel mix to start and run optimally. When a catalytic converter is clogged, the trapped exhaust gases negatively affect the amount of air and fuel in the engine. That is why starting the car becomes difficult. It might eventually start but suddenly the engine stop after sputtering for a bit. You might also notice that your car engine knocking while running slow. Engine performance issues are a symptom of clogged cat-con.

Fuel Efficiency Issues

A car with a clogged catalytic converter will become less fuel-efficient than it used to be. Here’s why. The trapped exhaust gases within the engine reduce the amount of air and oxygen that gets into the engine. When this happens, the car engine struggles to accelerate even when you have your foot on the gas pedal. As a result, your car engine consumes more fuel because it is forced to work harder.

Your Dashboard Lights Come On

This is one of the most prominent signs of a blocked catalytic converter. Clogged catalytic converters have the potential to trigger your car sensors that are designed to deal with any emission issues. For example, bad O2 sensors help you monitor the oxygen to exhaust gas ratio and the fuel-air mix so you can detect any emission issues with your car.

That’s why your car’s dashboard is a good place to look at if you suspect that your catalytic converter is clogged. Except you drive an antique, your car will have a diagnostic system that lets you know when there are issues with your car. So if you notice that the engine overheats the light comes on, then chances are that your catalytic converter has an issue. That’s not to say that your catalytic converter is clogged every time this light comes up. Rather, you’d be better at diagnosing the cause of the light coming up, because it is an indicator that your car engine is has a fault. And a clogged catalytic converter is one of the reasons for this.

Failed Vehicle Emission Tests

The next logical step after observing the check light on is to take a vehicle emission test because nothing is more indicative of a clogged catalytic converter than a failed vehicle emission test. The reason for this is that a functional catalytic converter is a crucial part of your car’s emission control system. If your car fails an emissions test, then it becomes clear as day that your car has a blocked catalytic converter.

The Smell of Rotten Eggs

A clogged catalytic converter gives off a rotten egg smell which is indicative of the presence of Sulphur. This occurs when the catalytic converter can no longer catalyze pollutants effectively because it is clogged. Bottom of Form

How To Diagnose a Clogged Catalytic Converter

The best way to be sure that your car has a blocked catalytic converter is to diagnose the car based on the symptoms you noticed. Thankfully, you can get some of the diagnostic tools you need online or at offline stores. That said, here are ways that you can diagnose a clogged catalytic converter.

The Vacuum Test

To conduct this test, you will need a vacuum gauge and some help(optional). Here are the steps you should take to conduct this test:

  • Depending on the type of car, you want to set the transmission to park or neutral after which you apply the parking brake.
  • You then associate the vacuum gauge to a direct vacuum line like a direct intake manifold port.
  • Start the car and let it idle until it gets to its operating temperature. The vacuum gauge should be somewhere around 18 and 22 in-Hg at this point.
  • Maintain a speed of about 2500-3000rpm while you watch the vacuum gauge. Its reading should drop for a bit before returning to its former level in a matter of seconds. If it takes forever for the reading to return to its former level, then it’s very likely that you have a blocked catalytic converter.

The Back Pressure Test

You will need a back pressure gauge for this test, and the site of the test is the exhaust system. Here is how you conduct this test:

  1. Remove the front oxygen sensors
  2. Replace it with the backpressure gauge
  3. You then start the car and pay attention to the reading from the pressure gauge. Anything between 0-3 psi is normal especially when you increase the speed to around 2500 rpm. A reading that is about 8 psi or more means that your car has a clogged catalytic converter.

The Temperature Test

To run a temperature test on your car, you will need thermometers (infrared or kitchen). Here’s how to conduct the test.

  • Start the car and let it get to operating temperature (you could take it for a short drive or just let it idle for some 20 minutes).
  • Ensure that it is on a flat area,
  • Depending on the type of car, set your transmission to “Park” or “Neutral.”
  • Get and note the temperature reading of the inlet pipe which connects to the front of the catalytic converter. You might have to raise your car to do this.
  • Repeat same for the outlet pipe which connects to the rear of the catalytic converter. If the front temperature is at least the same as the rear temperature, then there is some issue with the catalytic converter.

How to Unclog a Catalytic Converter

At this point, you are sure about the state of your catalytic converter, and you are probably looking for a quick fix for the catalytic converter. The good news is that there are two ways for you to unclog your catalytic converter. However, here are some things you need to bear in mind.

It would be best if you ascertained that the catalytic converter is not clogged beyond repair. You also want to be sure that it is not broken. If your catalytic converter is in any of these states, then you might want to get a mechanic’s help because applying a DIY approach might be futile. Once you have cleared that you can opt for any of these methods of unclogging your catalytic converter.

Unclogging the Catalytic Converter without Removing It

There is a caveat for this method. It only works when the catalytic converter is not seriously clogged. You will need a catalytic converter cleaner.

This method is also great for cleaning your exhaust and fuel systems as well as your oxygen sensors. Here’s how to go about it:

  1. Get a catalytic converter that works well with your car.
  2. Ensure that you have about 15 liters of fuel in your tank
  3. Follow the instructions on how to use catalytic converter cleaner with regard to the fuel/catalytic converter cleaner ratio
  4. Pour the catalytic converter cleaner into the fuel tank.
  5. Drive your car at 2500rpm(at least) for about 30minutes. The aim is to drive for long enough for the catalytic converter/fuel mixture to go around the car and clean the system. But make sure that the car does not overheat while on this drive.
  6. Re-calibrate the OBD code after which your re-read the catalytic converter

If at the end of the ride you notice that the car accelerates quickly and there is less black smoke from the exhaust, then you might have unclogged the catalytic converter. It is one of the cheapest ways to fix a catalytic converter. You might want to be wary of how you use some brands on which the jury is still out. Say, for example, the seafoam catalytic converter cleaner.

Unclogging the Catalytic Converter by Removing It

You should only undertake this method when you have tried the first method, and it didn’t work out. Here are the tools you will need:

  • Some automotive degreaser
  • A large container
  • Some penetrating oil
  •  A Floor jack
  • Jack stands
  • An impact wrench
  • A pressure washer

Here’s how you go about this method:

  1. Let the exhaust system cool down to avoid getting burnt.
  2. Jack up the car and keep it suspended with jack stands
  3. Take out the oxygen sensor(s)
  4. Apply some penetrating oil to loosen the bolts.
  5. Inspect the catalytic converter after removing it. If you hear a loud rattle, then you might want to stop because the components of the catalytic converter are most likely in pieces. If you don’t hear anything, then you should continue with the process.
  6. Use the pressure washer to wash the catalytic converter at low pressure.
  7. Immerse the catalytic converter in hot water and degreaser.
  8. Rinse the catalytic converter with the pressure washer at low pressure.
  9. Reinstall the catalytic converter after it has been allowed to drain and dry.
  10. Reinstall the oxygen sensor(s) after the catalytic converter is back in its place.

FAQs:

Q: Can A Clogged Catalytic Converter Be Cleaned?

Yes, but it all depends on the level of clogging. A slightly to the averagely clogged catalytic converter can easily be cleaned. In such an instance, the clogging is mild and can easily be removed by fuel additives or by manually washing the catalytic converter.

However, there are extreme cases where an overly clogged catalytic converter is best replaced because it might be clogged beyond repair. In such a situation, you will find that the exhaust has heated the catalysts to the point that they melt and can no longer catalyze the emissions from the exhaust. Another situation is when the internal parts of the catalytic converter have come apart either because of physical impact or heat.

Q: How Do You Fix A Clogged Catalytic Converter Without Replacing It?

Replacing a clogged catalytic converter can be quite expensive. Thankfully there are two ways to go about fixing a clogged catalytic converter without having to replace it:

Cleaning It Without Removing It: Here you try to unclog the catalytic converter using a combination of fuel and a catalytic converter cleaner. After mixing both elements in your fuel tank, you drive the car around at a relatively fast spend for an extended period. The fuel and the catalytic converter cleaner circulate throughout the car and flushes out the pollutants.

Cleaning It After Removing It: This is a more complicated method that involves removing the catalytic converter and manually washing it. It is then reinstalled after it has been drained and dried. This method should only be tried as a last resort.

Q: What Are The 3 Most Leading Failures Of A Catalytic Converter?

Catalytic converter failure can be troublesome for both you and the car. It hampers the driving experience and can drain your pockets too. It can also lead to engine failure if you don’t manage it on time. Here are the 3 most leading failures of a catalytic converter:

  • Mechanical Damage
  • Overheated/Broken Catalytic Converters
  • Coated Substrate

Q: Can I Hit My Catalytic Converter With A Hammer?

Yes, you can. Part of the diagnostic process will require you to use an unclog catalytic converter hammer to test the structural condition of the catalytic converter. Every catalytic converter contains a substrate that can disintegrate due to physical impact or overheating.

If you hear a rattling sound when you hit the catalytic converter with the hammer, then the substrate has disintegrated, and the catalytic converter should be replaced not unclogged.

Q: Can I Put Cataclean In Full Tank?

Not if you want to get the best outcome. For one, putting some Cataclean in a full tank will cause the tank to overflow. Secondly, the mixture of fuel and Cataclean will not be “strong” enough to clear the pollutants. To get the best results from using a Cataclean catalytic converter cleaner, you do not want to put it in a full tank of fuel. The recommended quantity of fuel for best results is about 15 litres.15 liters of fuel will allow just the right concentration of Cataclean that is required to unclog your catalytic converter.

Easiest Catalytic Converter Cleaning And Inspection – YouTube

Final Words

You need not worry too much about catalytic converter-related issues once you know how to unclog a catalytic converter. You could easily apply any of the two methods described in the article to unclog your catalytic converter. Unclogging your catalytic converter without removing it is the more manageable, and cheapest way to fix a catalytic converter. However, it is just a quick fix for a catalytic converter and is not as effective as unclogging the catalytic converter after removing it.

Both methods are great for unclogging catalytic converters for different reasons. However, there are scenarios where catalytic converters cannot be unclogged because of the level of damage. When this happens, your best bet is to replace the catalytic converter.

Osuagwu Solomon

Osuagwu Solomon is a seasoned automotive technician for the past 9 years, and a technical writer. He loves writing about auto professional repair guides, DIY repair guides, and buyer’s guide. After spending six years in the automotive workshop, he decided to impact his knowledge to people aside his domain, and he has achieved this by centering his Automotive writing skills on REPAIRS.

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