What does a bad catalytic converter look like

Your vehicle’s catalytic converter serves an important role: it transforms chemicals created during the combustion process from hazardous to harmless, thus reducing air pollution. It achieves this remarkable feat thanks to a honeycomb mesh that is coated with a catalyst. Through a chemical reaction, this catalysts converts the chemical makeup of the emissions. While catalytic converters are designed to last for the lifetime of a vehicle that doesn’t always happen.

Over time, residue from the exhaust gases a cat is rendering harmless build up within its honeycomb-shaped interior. Sometimes, so much residue builds up that the catalytic converter clogs and stops working. If this integral part fails, your vehicle will spew hazardous emissions into the environment and you may not even know it — until your vehicle fails its next inspection.

• Your vehicle’s check-engine light is on, and you’re not sure why. When your check-engine light illuminates, “catalytic converter problem” is probably not your first suspicion. If you rule out other causes of an engine-misfire, oxygen sensor, or emissions-related code, have a repair technician check your cat.
• You smell rotten eggs. Fuel contains sulfates, which are characterized by that stinky rotten egg smell. A clogged cat causes fuel to build up, making the usually undetectable odor noticeable.
• The exhaust smoke coming out of your car’s tailpipe is dark. A clogged cat makes it more difficult for exhaust to exit your vehicle, so it builds up and is thicker and darker when it comes out.

• Your vehicle’s gas mileage has decreased noticeably. Experiencing pain at the pump? That, combined with other symptoms, could point to a catalytic converter failure. A clogged cat causes reduced airflow that causes your engine to burn extra fuel. Not only does this increase your fuel bill and waste gas, it makes the clog worse. To the average driver, lower fuel efficiency is one of the most noticeable symptoms of a bad catalytic converter.
• Your vehicle is misfiring. Catalytic converter problems cause gas within your engine to heat up to the point that it actually ignites. This ignition is what causes the misfiring sensation – and that can destroy engine components. Anytime your vehicle misfires, you should have it checked out by a reputable service professional.
• You remove oxygen sensors and vehicle performance plummets. If you happen to know your way around under the hood (or better yet you know a great mechanic) you can run a test. Remove your car’s oxygen sensors from the exhaust system (temporarily). If performance worsens noticeably, that’s a sure sign your catalytic converter is going bad.
• You hear a rattling sound coming from beneath your vehicle. A rattling sound coming from your car is never a good sign. When a catalytic converter becomes damaged, it can cause the honeycomb mesh interior to break or collapse. When you turn on your vehicle, these pieces will vibrate and make a rattling sound.

An Ounce of Prevention…

Unfortunately, if you discover your catalytic converter has failed it cannot be repaired and must be replaced. Replace it sooner rather than later to avoid contributing to air pollution, and to avoid potential collateral damage to your engine and exhaust system. Replacing a catalytic converter isn’t cheap. By one estimate, most replacements will cost between $1,300 and $1,600. A better option? Be diligent about preventive maintenance. Keep your exhaust system clean and well-maintained so you can avoid catalytic converter problems in the first place.

The catalytic converter’s main job is to convert car exhaust's bad emissions and pollutants into compounds that won’t harm the environment. In the metal canister itself, platinum and palladium — metals that act as chemical catalysts — coat a ceramic honeycomb or ceramic beads in the casing attached to the exhaust pipe.

Here, carbon monoxide is converted into carbon dioxide, hydrocarbons into carbon dioxide and water, and nitrogen oxides back into nitrogen and oxygen.

Usually, a catalytic converter will last throughout the car’s lifetime, but sometimes it can go bad and will need replaced. Typically, this happens in older cars when the catalytic converter becomes clogged. As a result, the vehicle’s exhaust gases can’t get through to the muffler and then out of the car. Over time, your car can also use all the metals that act as the catalysts in the converter, which can cause the converter to fail.

How do you know if your catalytic converter needs to be repaired or replaced? Here are five common symptoms of a bad or failing catalytic converter.

#1: You fail your emissions test.

In most states, including Ohio, your vehicle’s emissions must be checked annually to make sure everything is working properly. The catalytic converter is your car's main component responsible for controlling engine emissions. An increase in the level of carbon emissions coming from your exhaust is a common sign that your catalytic converter may be failing. This can be from things like antifreeze or motor oil contaminating the chemical mechanisms inside the catalytic converter.

#2: Your check engine light is on.

Your on-board diagnostic system — which comes standard in all cars and trucks manufactured since 1996 — tests the catalytic converter automatically. Oxygen and air-to-fuel ratio sensors monitor the efficiency of the catalytic converter by monitoring the gas levels in your exhaust. If too much pollution is coming out of your tailpipe, your check engine light will come on.

The most common reason for a catalytic converter to fail is because a related part fails — most often, a faulty spark plug. (Bad plugs can cause unburned gas to overheat inside the catalytic converter.) These plugs are inexpensive and easy to replace, so if you have a bad spark plug, be sure to take care of it before it causes damage. Read our blog post on the topic to learn how (and when) to change spark plugs.

#3: Fuel efficiency drops suddenly.

If you notice a sudden decrease in your gas mileage, it could be a sign of a clogged catalytic converter, or perhaps a faulty one. When your engine gets less oxygen — or when there is resistance in the exhaust path — your engine has to work harder, which ultimately consumes more fuel, causing you to get fewer miles to the gallon.

#4: When you push the gas pedal, you don’t go any faster.

Reduced engine performance is a red flag that there might be something wrong with your catalytic converter. When exhaust gets trapped in front of the catalytic converter, it can cause your engine to run less efficiently.

This increased back pressure can actually cause your engine to stall completely. Your vehicle may jerk or act as if there is an air lock in your system. Often, the car will feel like there is no fuel reaching the engine when you push the gas pedal.

#5: Your car doesn’t start easily — or at all.

If the catalytic converter is clogged and exhaust gases can’t get through to the muffler and out the back of the car, it can cause your engine to stall from increased exhaust back pressure. If your car runs normally for a few minutes after you start it, but then it starts sputtering or stalls out altogether, it could be your catalytic converter.

If you think your catalytic converter might be going bad, it’s important to have a mechanic take a look before the problem gets worse and leads to more extensive and expensive damage to your exhaust system. Your mechanic can check your emissions to see if the catalytic converter is clogged, or he can remove it and then check the change in your engine’s performance.

Sometimes, when a clogged converter is suspected, your mechanic can temporarily remove the oxygen sensor from the exhaust pipe in front of the catalytic converter and look for any changes in performance as a result.

The catalytic converter requires the right mix of exhaust gases at just the right temperature. Anything that causes the mixture or temperature to change can cause the converter to work less efficiently and fail faster.

Are you having trouble with your emissions and think it might be your catalytic converter? Are your exhaust sensors working properly?

How do I know if my catalytic converter is bad?

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What does a failing catalytic converter sound like?