Catalytic Converter Damage: Signs, Causes, and How to Avoid Costly Repairs
When your catalytic converter, a key part of your car’s exhaust system that turns harmful gases into less toxic ones. Also known as a cat, it’s not something you think about until it fails—and then it’s usually too late. A damaged catalytic converter doesn’t just trigger a check engine light. It can choke your engine, burn through fuel faster, and even overheat to the point of starting a fire under your car.
This isn’t just about emissions. Your exhaust system, the full path that carries engine gases out of the car relies on the catalytic converter to keep pressure balanced. If it’s clogged or melted, backpressure builds up. That forces your engine to work harder, which kills power and mileage. You might notice your car feels sluggish, especially when accelerating. Or worse—you hear a rattling noise from under the car, which often means the internal honeycomb structure has broken loose.
What causes this? Often, it’s something simple you ignored. A misfiring spark plug dumps raw fuel into the exhaust. That fuel ignites inside the cat, overheating it until the ceramic core melts. Bad oxygen sensors, oil burning from worn piston rings, or even using the wrong fuel can do the same. And if you’ve been driving with a faulty engine, the core component that burns fuel to create power for months, the cat pays the price.
You don’t need a diagnostic tool to spot trouble. If your car smells like rotten eggs, that’s sulfur from unburned fuel passing through a failing cat. If your MOT fails on emissions—despite a clean engine—you’re likely looking at cat damage. And if your car suddenly loses power after a warm-up, it’s not your transmission. It’s the exhaust choking.
Replacing a catalytic converter isn’t cheap. But fixing the root cause? That’s the real savings. Many people replace the cat and then the same problem comes back because they didn’t check the spark plugs, fuel injectors, or oxygen sensors. The posts below show you exactly how to spot the early signs of trouble—before your exhaust turns into a paperweight. You’ll learn how worn brake pads, bad spark plugs, and even a clogged air filter can indirectly wreck your catalytic converter. These aren’t guesses. These are real fixes from UK drivers who’ve been there.
