How to Tell if Catalytic Converter Is Clogged (Quick Fixes)

Driving with a clogged catalytic converter is uncomfortable and even unsafe. Your car can shut off on the go, or its engine can catch fire. Learn how to identify if your converter is faulty at the early stages.

"How to tell if a catalytic converter is clogged?" you ask. These are 5 signs that show it probably is.

• The check engine light is on
• The car vibrates when starting
• You can't accelerate normally
• You notice increased fuel consumption
• You have rotten eggs smell from the exhaust pipe.

Check for more details about each symptom below and learn if unclogging a catalytic converter is possible.

5 Symptoms of a clogged catalytic converter

A clogged catalytic converter doesn't stop harmful substances from flowing into the atmosphere, which can cause acid rain and smogs.

Also, a malfunctioning catalytic converter makes your engine overheat, resulting in costly repairs. So it's better to know the signs of problems with this exhaust system's component, and below are the main ones:

The check-engine light is on

When the little engine icon lights up, any driver would feel worried. That's because it signals severe issues with your vehicle, and unfiltered emissions are one of them.

The two oxygen sensors attached to the converter continuously check the composition of the released substances.

Once the concentration of the unburnt oxygen drops or increases, compared to the standard air-to-fuel ratio, the sensors report the problem. That's when the ECU (Electronic Control Unit) lights up the engine error on the dashboard.

You will know if the converter is the cause once you connect the OBD (On-Board Diagnostics) scanner or visit the auto repair service. You'll usually get a P0420 or P0430 error.

The car vibrates when starting

When the pores of the converter get dirty and narrow down, exhaust gasses can't go out of your engine properly. In other words, the converter blocks the holes, and your engine gets short of breath.

This results in unpredicted pressure outbursts, which cause vibration at starting. In severe cases, when the emissions are poorly ventilated or not released, your car may not start.

Also, you can experience car jerking, which becomes more frequent. Such a condition is dangerous as the vehicle can suddenly shut off on the go.

You can't accelerate normally

As mentioned above, insufficient flowing out of exhaust gasses affects your engine performance. So poor acceleration is another tell-tale sign the converter is dirty.

Low fuel pressure increases the lag between pressing the gas pedal and speeding up. You'll also notice that climbing hills becomes harder.

The honeycomb material inside the converter can also break, clog the pores, and block the emissions. In this case, you'll hear rattling noises and feel the heat from under your car. These symptoms are dangerous as they appear when your engine overheats.

You notice increased fuel consumption

The oxygen sensors near your converter allow the engine to supply the balanced mix of fuel and O2. A faulty converter doesn't release oxygen, which provokes more gas input.

This way, your fuel bills grow while the converter becomes more clogged. Moreover, unburnt fuel gets into the cat converter and ignites there. It ruins the chemical mix and structure of the inner material.

This leads to more blockage and improper functioning of the entire combustion system, which exhausts your engine even more.

You have a rotten eggs odor from the exhaust pipe

A clogged catalytic converter is one of the two elements in your vehicle that can produce a rotten egg smell. (The other is the leaking battery). You can sniff it from your exhaust pipe when sulfur burns.

When petroleum gets to the engine, it burns, producing a harmful gas called hydrogen sulfide. In the converter, it's decomposed into sulfur dioxide that has no odor.

But when the pores get clogged, hydrogen sulfide, which smells like bad eggs, goes out of the tailpipe unprocessed.

Can I drive with a clogged catalytic converter?

Once your converter is partly clogged, you'll be able to drive. However, the symptoms will worsen, and your car may not start one day. Moreover, your engine can overheat while driving and even catch fire.

On the other hand, faulty exhaust systems harm the environment. So you can get a fine or fail an emission test required to re-register your vehicle. That's why going to a car service is a reasonable plan.

Why converters get clogged: 3 reasons

Catalytic converters stop working normally because of the following:

• Damaged or worn spark plugs. Bad plugs don't fire the engine's cylinders, allowing unburnt fuel to leave the combustion chamber and enter the catalytic converter. High temperature inside the converter ignites the gas, which burns the protective cover and destroys the honeycomb structure and chemical agents.
• Antifreeze or oil getting to the exhaust system. These liquids are dangerous for the converter because they cover its inner layer. Also, they build soot deposits on pores, preventing normal airflow. This creates excessive pressure, which takes exhaust gasses back to the combustion chamber and causes engine overheating.
• Malfunctioning oxygen sensors. Incorrect information from O2 sensors makes the fuel mixture too rich or lean. The more-gas one will burn the catalyst cover inside. The less-gas mix will prevent the converter from properly decomposing hydrocarbons into harmless elements.

How to unclog a catalytic converter without removing it

Below, you'll learn how to clean your cat converter without raising your car on jack stands, removing oxygen sensors, and using pressure washers.

Still, remember that this method works only when your converter is moderately clogged. Also, this approach can be ineffective or less effective than professional unclogging.

You'll need to buy a catalytic converter cleaner and add the liquid directly to your fuel tank. It must be ⅓ full, which is approximately 4 gallons of gas.

Pour the cleaner and drive for 30 minutes at 2,500+ RPM to let the liquid reach the converter. After that, you might notice the symptoms disappear.

How to tell if a catalytic converter is missing

The signs of a missing cat converter are similar to those of a bad one. They include smelling and smoky exhaust, bad engine performance, and check-engine light appearance.

However, when your converter is missing, there's one more symptom that is easy to identify. It's the loud sound coming from the muffler.

Once you hear it, look under your car. It might have been stolen if you don't see a metal canister connected to the muffler. It often looks like a "flattened loaf of bread."

The bad news is driving without a cat converter is illegal; the good news is that your insurance will probably compensate you for buying a new one.

Final words

When your car accelerates poorly, consumes a lot of fuel, vibrates at the start, or smells like rotten eggs, your catalytic converter might be clogged. With time, it can lead to engine blocking.

So, if you notice these annoying symptoms, try to use a cleaner or contact a repair service and schedule a visit.