How to Unblock a Clogged Catalytic Converter

Loss of power, sluggish, over heating, stalling, check engine light on and very little exhaust pressure coming out the tailpipe to name a few are signs of a possible clogged catalytic converter.

This essential component of your exhaust system can become blocked due to various reasons, leading to reduced engine performance and increased emissions.

What is a Catalytic Converter?

A catalytic converter is basically an exhaust emission control device. It converts toxic exhaust gases into somewhat safe or less toxic gases by a redox ( reduction-oxidation ) reaction.

Primitively categorizing, catalytic converters are of two types:

Two - Way Converter

• Two primary reactions takes place:
• It oxidizes the Carbon monoxide to Carbon dioxide.
• It also oxidizes Hydrocarbons ( unburnt / partially burnt residues in exhaust ) to Carbon dioxide and Water.

Three - Way Converter

• Three primary reactions takes place:
• Apart from the above mentioned two primary reaction one additional reaction takes place :
• Reduction of Nitrogen oxides NOx into Nitrogen and Oxygen.

Signs of a Clogged Catalytic Converter

Generally you will experience a degree of the following:

1. Loss of power, which becomes greater with vehicle speed.
2. A smell of sulfur (although this can happen in normal operation as H2S is created during the catalytic reaction)
3. Engine overheating
4. Poor fuel economy
5. In most, but not all cases, a check engine light. The MIL may be for a P0420/P0430 but not always. If the PCM detects a misfire, it will suspend the catalytic converter monitor, so no code is set and no MIL, or at least no MIL with an associated catalytic converter efficiency code. Some might say it will set a misfire code, and that may be true…but I would cite Ford as an example of not setting codes.

In short, performance and economy both suffer, and your engine will run warm/hot/may overheat.

The only way to find out if the catalytic converter is clogged is by removing the upstream oxygen sensor and screw in a pressure gauge. Anything over 2 psi whilst stabbing the throttle is too much.

The pcm monitors catalyst efficiency by comparing oxygen sensor readings, one before and one directly after the converter.

When the readings mirror each other like the graph on the left the pcm determines the catalyst is non functioning and sets a pending code but does not turn on the cel . Only after consecutive failures does the check engine light illuminate. These monitors can take several days or 100 or so miles of driving to perform.

Why does a catalytic converter clog

Converters rarely die, they are usually killed. The number one killer? Misfire, namely ignition misfire. Ignition misfire sends raw fuel and air to the converter which then proceeds to convert it, releasing a lot of heat energy and eventually (and quite quickly) destroying itself.

Can You Unclog a Catalytic Converter?

Unfortunately, it's usually not possible to unclog a catalytic converter. They don't clog, they melt into a ball of solid mass. I’ve read online that you can clear it by removing the unit and soaking it, but for whatever reason I’m skeptical.

This doesn't work and so, don't waste your time.

You can cut it open, or off, and knock the stuff out of it, or put a pipe in its place depending on where you live, you might be breaking the law and wouldn't be able to pass an emissions test.

But the best of all solutions, is having a new catalytic converter, but most importantly, you'll also need to find out what caused it to fail because they never fail on their own. Engine misfires, internal engine oil or coolant leaks, poisoning by silicone, impact, or cold shock are what kills them. If you don't find out what killed yours, you'll just kill the replacement cat. However, in some cases, using a specialized fuel additive "MIGHT" help temporarily, but the best solution is typically to replace the converter.

How to Prolong the Life of Your Catalytic Converter

1. Avoid Overheating: Always park your car on hard surfaces or areas with nothing flammable, away from long grass to prevent the catalytic converter from potentially igniting grass or other flammable materials.
2. Drive slowly over speed bumps or very bumpy roads to reduce the change of the exhaust system being grounded. This could cause impact damage to the catalytic converter.
3. Address warning lights: By paying attention to dashboard warning lights and addressing any issues promptly to prevent further damage of the catalytic converter. This is because Engine misfires accelerate catalytic converter failures and can be detected by a warning light. 
4. Never use exhaust paste in front of a catalytic converter when fitting. When the exhaust paste hardens, it can break off in chunks and damage the monolith. Paste dust can also block the monolith.
5. Always use the recommended fuel and oil for your vehicle to ensure optimal performance and protect the catalytic converter.
6. Be watchful about the fuel additives you are using in your car, as some can harm the catalytic converter.
7. Never attempt to bump or tow start your car. This causes unburned fuel to be injected into the catalytic converter which can make the monolith overheat and melt.
8. Don't tow loads that are too heavy for your vehicle. For example, an overloaded caravan will actually push a car along when it travels downhill. This sends unburned fuel into the exhaust system and can cause the monolith to overheat and melt.
9. Schedule regular maintenance according to the manufacturer's recommendations to ensure your engine is running efficiently and protecting the catalytic converter.
10. Be mindful of driving through deep water or snow, as sudden temperature changes can damage the catalytic converter.

Replacing a Catalytic Converter

Replacing a catalytic converter can be expensive, but it's often necessary to restore your car's performance and emissions. If you're experiencing symptoms of a clogged catalytic converter, it's best to consult with a mechanic to get a proper diagnosis and discuss your options.

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