Symptoms Of Bad Catalytic Converter

The symptoms of bad catalytic converter are pretty easy to determine most of the time. Most of these signs are very common occurrences when there is something going on with the cat or exhaust system of the vehicle. If you are aware of what some of these symptoms are then it will make it a lot easier to diagnose the problem and then getting it fixed in a timely manner before more problems arise. The sooner it can be found and fixed the less expense you are likely to be out.


Exhaust Problems

If your car is producing particularly black or dark exhaust smoke from the muffler or exhaust system, it could be because of a substantial amount of carbon buildup in your car’s engine or a bad catalytic converter. If you perform regular maintenance on your vehicle, and use a quality gasoline additive or premium unleaded fuel, the culprit is probably a defective catalytic converter that will need to be replaced.

Poor Performance Issues

A faulty catalytic converter can also cause your car to perform less efficiently and produce far lower levels of power. If you experience an inability to drive at normal speeds even when giving the car a lot of gas, there’s a good chance that a bad catalytic converter is the problem. The car may also experience a lot of jerking and jumping when accelerating for no apparent reason as well.


Use Your Nose

One of the surest ways to tell if your car is catalytic converter is bad is to simply use your nose. A faulty catalytic converter will often produce a horrible smell that smells like a combination of rotten eggs and sulfur. The smell is hard to miss, and almost always a sign you need to replace the defective catalytic converter in your vehicle.




One of the most common symptoms is many times overlooked. But it is very likely that when the cat is having trouble you will smell a foul odor coming from the car. It smells like a rotten egg. It occurs because the unit is failing to remove enough of the sulfur from the exhaust before it is expelled.


When Your Catalytic Converter Cries For Help


A catalytic converter has an easy job when it’s in good condition: exhaust gases pass through the unit and are converted by a chemical reaction between the gas components and the surface of the unit. A faulty catalytic converter, however, robs your car of performance and dumps pollutants into the atmosphere. Here’s how to tell the difference:


  • I feel a headwind. If your vehicle has little accelerating power, or it feels like you’re driving into resistance, this could be a sign that the catalytic converter is plugged. A plugged converter is typically a sign that your vehicle may have fouled sparkplugs or a burned exhaust valve. These problems allow unburned fuel into the exhaust system, where it accumulates in the catalytic converter.

  • Where did all the gas go? A sudden and noticeable drop in fuel efficiency may also be a sign that the catalytic converter has become plugged.

  • What’s that smell? A sulfur or rotten egg smell coming from your exhaust is a sign of a too-rich fuel mixture-the extras fuel in the exhaust is plugging the catalytic converter.

  • Epic fail. If your car fails an emissions test (commonly given during vehicle inspection), this is sign that the catalytic converter is fouled. Fouling occurs when a contaminant coats the inner surfaces of the unit, blocking the chemical conversion from occurring. The color of exhaust smoke can be used to tell which contaminant is fouling the converter. Blue smoke indicates the presence of phosphorus, which comes from burnt motor oil. White smoke indicates the presence of silicon, which comes from burnt engine coolant.



Many times you may notice some catalytic converter problems if your car seeming to have no power all of a sudden. This may display in a couple of different ways. For one thing, when you try to pass another vehicle it will seem like the car is having to work very hard and still not having enough power to get on around it fast enough. The other way is that the car will lose power when it is idling or if the engine is too cold. Sometimes the car that is having some problems with the exhaust system will just stall for no reason at all.


Alien Chemicals in the Converter


Contamination of the chemical mechanisms inside the catalytic converter, caused by the addition of substances such as motor oil or antifreeze can prevent the converter from performing correctly. You will notice a raised level of carbon emissions from the converter if this happens and you will need to replace the converter before it does damage to your entire exhaust system or emits an illegal amount of emissions into the atmosphere.



Keeping a close watch on your gauges may also give you a hint that there is a problem of some sort going on. For one, you should be aware of what the temperature gauge reads normally. If you notice that it tends to be running a little hotter than normal, it is a good time to get the exhaust system checked. Many times the cat is clogged and therefore because of the back-up the engine overheats.  The other gauge to watch is the O2 sensor. This is a light that comes on if there is too much oxygen in the exhaust of the car. If either the temperature gauge shows a higher temperature or the O2 light comes on you should get the vehicle checked by a professional mechanic.


The failure of a catalytic converter typically happens for one of four reasons. The first is overheating. This results when fuel gets into the converter, usually from misfiring spark plugs, and burns out the mechanisms inside. Catalytic converters are not designed to handle the heat of burning fuel; when fuel starts to burn in the converter, it can cause a great deal of damage to the converter and the rest of the exhaust system. One of the noticeable symptoms of overheating in the converter is a significant loss of power from the engine. Another converter failure is a contamination of the chemical mechanisms. In some cases, motor oil or antifreeze can find their way into a catalytic converter and prevent the converter from being able to perform its chemical reactions. A common symptom of this kind of failure is a raised level of emissions that could reach the point of being illegal. A hot catalytic converter needs to cool down before it can be exposed to a cooling agent such as cold rain or snow. If a hot converter is hit by snow, ice or cold rain, this could crack the shell of the converter and begin to cause a rattling sound. The final type of failure is simply running over a rock and having it impact the converter, or any other type of physical damage that could occur during the course of driving. Depending on where the converter is damaged, one of the symptoms of physical damage could be raised emissions or a drop in engine performance.



It might save you quite a bit of money if you keep ahead of some of these bad catalytic converter symptoms.