You should always stay aware of the symptoms a problem exists with your car so that you can fix it before it becomes a bigger problem.
Catalytic converters are known to fail and can be very expensive to replace, especially if you want a brand-new one.
So figuring out if you have a bad catalyst is crucial, so you don’t end up replacing a catalytic that is completely fine.
In this post, I am going to go over the most common bad catalytic converter symptoms, the location of where the catalytic converter is, what is its function, and what makes it so desirable for thieves.
What is a catalytic converter?
The catalytic converter is part of the exhaust system. This device contains catalysts that assist in converting the car’s damaging pollutants into less harmful compounds. The basic structure of the device is shaped like a honeycomb.
The honeycomb shape helps the pollutant gases maximize the amount of surface area they react with while converting Nitrogen oxidises, carbon monoxide and hydrocarbons into less harmful gases like carbon dioxide.
Platinum, although commonly the most expensive material used, is typically used as the catalyst. In particular instances, rhodium and palladium are also used.
All burnt gases flow at approximately 800 degrees through the exhaust pipe as combustion occurs in the engine, through the catalytic converter which impacts the exhaust gas flow from the engine.
Perfect – New car catalytic converters can last typically 10 years. As other catalytic converters age, the honeycomb structure of the catalytic converter will eventually congest and suffocate, impacting engine performance.
Catalytic Converter Location
The catalytic converter is located on the exhaust pipe system, between the muffler and the exhaust pipe manifold.
Depending on your car engine, the length it is mounted from the engine can vary significantly.
On some engines, the catalytic converter is right off the exhaust manifold where it connects to the engine, while with others, it can be anywhere from 12 inches (30cm) to 60 inches (152cm) from the engine to the converter.
Symptoms Of A Bad or Clogged Catalytic Converter
The most common signs of a bad catalytic converter are the sulfur smell when the engine is warm and the check engine light is on your dashboard.
You might also notice engine performance issues like acceleration lag, fuel consumption issues (high or low), and engine misfire.
While not all symptoms, they are definitely the most common. Here is a more thorough list of symptoms of a bad or clogged catalytic converter to watch for:
#1. Check Engine Light.
The check engine light, an evident sign of an issue with your car, is also a strong sign of a bad catalytic converter. When you have a compatible OBD scanner checked, a catalytic converter trouble code will show up that you can decode with the operating manual.
The most common trouble code for a bad catalytic converter is the P0420 code.
#2. Acceleration Lag.
If you experience delays when accelerating or lose power in steep areas and everything else such as spark plugs, filters, sensors, etc. is also ok. The problem may be a bad catalytic converter.
These symptoms can often be misdiagnosed by mechanics as other faults of oxygen sensor or something similar.
To see if the catalytic converter is clogged or faulty, place your hand just above the tail pipe end, tap the accelerator pedal to bring RPM to about 2000.
You should feel a decent amount of exhaust coming out if everything is operating properly. If it’s weak or a tiny puff, you may have a clogged catalytic converter. Comparing exhaust flow with another car similar to yours can also help in diagnosis.
#3. High or low fuel consumption.
Gas mileage can improve or worsen, a sign of a bad catalytic converter. While better gas mileage seems like a good scenario, it can damage your engine, which will lead to even more expensive repairs.
Improper combustion of the fuel from the exhaust getting blocked will make the car engine very less efficient and need to work harder for the same amount of power.
Thus, a bad catalytic converter will usually cause a higher fuel consumption (though lower can be possible in some cases).
#4. Smell of sulfur.
A clogged catalytic converter restricts exhaust flow too much so that engine air-fuel mixture gets rich (too much fuel and unburnt fuel).
The excess air-fuel mixture combusts producing a smell like rotten eggs or burnt sulfur; this is a distinct indicator of a defective catalytic converter.
#5. Discolored Housing.
If the catalytic converter housing is blue or otherwise colored, it could signify that the catalytic converter is excessively clogged and is producing excessive heat.
Excess heat can also occur if your engine is not working properly and unburnt fuel is reaching the catalyst. The fuel/oil mixture will ignite inside the catalytic converter if there’s enough heat and can melt any internal material, causing further more blockages.
If your catalytic converter is excessively clogged, the excessive heat buildup can also damage the engine and possibly other parts of the engine pretty quickly. Therefore, you should not drive your vehicle if you suspect the catalytic converter has failed.
#6. Starting Issues.
A clogged catalytic converter will make the engine receive excess fuel that the engine cannot combust. A clogged converter will create back pressure that will cause the motor to have difficulty getting rid of the exhaust.
If your car starts then dies after 2-3 seconds, it could very well be a clogged converter as it could take 2-3 seconds for the exhaust system pressure to build up to a point where the engine gets choked out and stalls.
#7. Increased Emissions.
If your catalytic converter is damaged or clogged, then it may not be doing its job any longer.
This will increase your emissions from the car engine. The overall purpose of a catalytic converter is to clean bad emissions, so that should be obvious.
You will likely see this by seeing dark exhaust smoke come out of your exhaust pipe while you accelerate or if you are just idling at a stop. If you have a yearly car inspection in the state or country you reside, your car will have a good chance of failing an emission test or smog test.
#8. Engine Misfires.
If a catalytic converter is clogged, it will restrict the oxygen flow to engines, which engines need a lot of for proper fuel combustion.
Restricting airflow can cause overheating due to an excess of unburned gases and is also likely to cause a misfiring engine.
If your engine is misfiring, you need to have it fixed immediately or you could face even more expensive repairs, just ignoring the issue will not give you a solution.
#9. Rattles or other noises.
The catalytic converter contains a honeycomb that can wear out and break into pieces or make a rattling noise. If you rev your engine, you will hear it rattling inside the catalytic converter.
You can get a friend to put the accelerator down while you listen under the car to see if you can hear any rattling from the catalytic converter.
Causes of Catalytic Converter Problems
Physical Damage
The catalytic converter (or converters, as there may be more than one in some vehicles) is located under the car between the engine and muffler, usually under the front seats or footwells.
This makes if susceptible to damage if you happen to drive over a curb or road debris, possibly damaging the muffler or tailpipe as well. Although you may not see it, damage could be visible when the car is on a lift, as it may happen during oil changes.
The sheet-metal heat shield surrounding the converter may get loose, causing it to rattle, but that’s really not an issue with the converter.
Crushing the catalytic converter will damage it, but even crushing the muffler or tailpipe may cause indirect damage to the converter (increasing backpressure on the exhaust is an increase in temperature inside the converter).
Overheating
A catalytic converter is responsible for converting pollutants, such as unburned gasoline and nitrogen oxide, from your vehicle’s exhaust into harmless gasses. However, if the catalytic converter is fed a lot of unburned gasoline, it will overheat and essentially melt the insides of it.
Restricting exhaust from a clogged or damaged muffler can result in the same. Either issue can ultimately cause the outside of the catalytic to get very hot, potentially resulting in the worst-case scenario of catching the interior carpet above it, or the grass below it on fire.
Clog or Contamination
The inside of a catalytic converter can become contaminated by unburned gasoline or coolant leaking into the exhaust through a bad head gasket, or engine oil leaking past the piston rings or valve guides that is burned with the air-fuel mixture in the cylinder.
If the engine misfires because of a fuel problem or faulty spark plugs, you can usually get your car computer to show you trouble codes to narrow down what is wrong. A diagnostic test, however, typically won’t show a mechanical problem such as a bad head gasket, or a major problem like worn piston rings or valve guides.
If engine coolant is leaking into the exhaust and contaminating the catalytic converter, you typically will notice white exhaust smoke. If the engine is burning oil due to a leak or other engine problems, you will typically notice blue or grey exhaust smoke. (A rich fuel mixture in the engine will typically show black smoke; that is, too much gasoline in the system will cause black smoke.)
Normally, the exhaust smoke is more prevalent when the car is being driven than when the engine is idling so the driver may not notice the problem until it gets really bad. It will help to periodically check the exhaust after the engine has been warmed up, but keep in mind that in cold weather you may see white smoke for a short period of time if the exhaust system has condensed water in the system that is being burned off.
If driving the vehicle causes the check engine light to come on, the driver may decide to ignore it because the engine does not seem to be affected. That is not a good idea because there are many reasons for the check engine light to come on.
Some problems that activate the light will be minor such as the gas cap was not tightened after filling, while others, such as replacing badly worn spark plugs, may be relatively cheap to fix today and keep cheap problems from causing a lot bigger problems, like ruining a catalytic converter, a year from now.
Age or Mileage
Catalytic converters can last 10 years or longer, if nothing else kills them earlier. But they will eventually just go bad.
Catalytic Converter Theft
Catalytic converters contain tiny amounts of palladium, platinum, and rhodium which are precious metals making them easy targets for thieves because scrap yards will pay well for a used catalytic conveter.
Catalytic converters are easy to steal because usually, all it takes is cutting off the pipe, using a tiger saw or similar tool and it’s usually done under 3 minutes.
Catalytic Converter Replacement
Replacing or repairing a catalytic converter often costs a lot more than it’s worth, particularly if the car is older.
Some workshops will replace the honeycomb inside the catalytic converter and reuse the outer bits. This may be worth it if the catalytic converter is expensive, but in most cases, it makes more economic sense to simply buy a new one.
Typically catalytic converter replacements cost between $400 and $2500. For more information on catalytic converter replacement costs visit Catalytic converter replacement cost.
FAQs.
Q: Can a bad catalytic converter ruin your engine?
Yes, but your engine will likely shut off and not run until the damaged catalytic converter is repaired.
A clogged or damaged catalytic converter can create high backpressure into the engine, which can damage other parts of the car’s engine or emission system, which can lead to an engine failure.
Q: What is the average life of a catalytic converter?
The average life of a catalytic converter is about 10 years or 100,000 miles.
However, there are many factors that affect the lifespan of a catalytic converter, including the type of vehicle it is in, the quality of the converter, and the vehicle’s maintenance.
Many catalytic converters will last the life of the car while others have a scheduled service for when the catalytic converter(s) is to be replaced.
Q: What does a bad catalytic converter sound like?
If you hear the catalytic converter rattling, it is likely bad. Sadly, there isn’t a specific noise out of the exhaust that would automatically suggest catalytic converter trouble.
Q: How do you fix a catalytic converter without replacing it?
If the catalytic converter is severely damaged, you will need to replace it or remove it and reprogram the ECU. For clogged catalysts, you can clean the catalyst.