“Gross! What’s that awful smell?” After driving your vehicle, you may notice a distinctive “rotten eggs” scent coming from your car. This is a classic sign that your catalytic converter is starting to fail. While “cats” have been on vehicles since the mid-1970s, many people don’t know what to look for when a catalytic converter breaks. Here’s some signs to watch for, and what to do about it.
HOW A CATALYTIC CONVERTER WORKS
Catalytic converters are efficient pieces of engineering, when they work. Maligned in the ’70s, the catalytic converter was partially blamed for the end of the classic muscle car era. While it was unfortunate that muscle cars went away for several years, the cat did its job, and the air over Los Angeles is no longer the color of baby food.
The catalytic converter works by breaking down unburned gases left over by the combustion process. Nitric oxide, carbon monoxide, and unburned hydrocarbons are all toxic to humans and can cause smog. After startup, the poisonous gases pass through the catalytic converter’s internal structure, which you can picture as a honeycomb design made of ceramic and coated in catalyst materials like platinum, palladium, and copper. At roughly 800 degrees Fahrenheit, the hot catalysts convert the gases into safer elements, like oxygen, carbon dioxide, and water.
WHY CATALYTIC CONVERTERS FAIL
In most cases, the catalytic converter will last for the entire life cycle of a vehicle…but not always. While sturdy, the catalytic converter can slowly fail over time as the catalyst elements wear out. High mileage is not the only culprit, as failure could be due to an improperly operating engine.
Worn spark plugs, or burned and leaking exhaust valves, allow unburned fuel into the exhaust system, where it ignites in the catalytic converter and melts the internals. A weak ignition system can also cause the same problem, by not getting enough spark to the plugs.
Catalytic converter problems could also be something more serious, like heavily worn piston rings or jumped timing chain. These problems allow fuel or air into the wrong place at the wrong time. A head gasket or intake manifold leak can cause problems too, as oil or coolant can coat the catalyst, setting off a check engine light. On some older vehicles, a flashing check engine light will be your tipoff to catalytic converter overheating, and it shouldn’t be ignored.
Keep in mind that the catalytic converter could fail again in a short time if an underlying issue is not fixed. Keep your ride tuned up, and your cat will live longer.
COMMON SYMPTOMS OF FAILED CATALYTIC CONVERTER:
Sulfur smell
Large fuel economy decrease
Failed emissions test
Check engine light
Discolored or warped outer housing
Noticeable lack of acceleration
Hard starting or no-start condition