The catalytic converter is a quiet part of the exhaust that does an important job: it turns harmful gases into less harmful ones before they leave the tailpipe. When it fails, performance drops and the check engine light usually appears.
What it does
Inside the converter, a honeycomb coated with precious metals triggers a reaction that reduces the pollutants in the exhaust. It needs the engine running correctly to work, which is why engine problems often kill converters.
Signs it is failing
- A check engine light with a catalyst efficiency code.
- Sluggish acceleration and poor fuel economy.
- A rotten egg or sulphur smell from the exhaust.
- A rattle from the exhaust if the internal honeycomb has broken up.
What causes failure
A converter rarely fails on its own. Long term misfires, burning oil or a rich fuel mixture overheat and clog it. Fixing the root engine problem first is essential, or a new converter will fail too.
Frequently asked questions
Can I drive with a bad catalytic converter?
A partially clogged converter lets you drive but robs power and fuel economy. A fully blocked one can stall the engine.
Will a fuel additive clean a catalytic converter?
A cleaner can help a mildly fouled converter if the engine is otherwise healthy, but it cannot fix a physically broken one.
For cleaners and performance parts, see our performance guides.
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