ASE A1 Engine RepairGeneral Engine DiagnosisEasy
A customer complains of a strong, pungent odor resembling rotten eggs coming from the exhaust. Which of the following is the most likely cause?
- AAn engine misfire
- BA lean fuel condition
- CA failing catalytic converter
- DA failing oxygen sensor
Show answer & explanationAnswer & explanation
Correct answer: C. A failing catalytic converter
A rotten egg smell from the exhaust is a classic symptom of a failing catalytic converter, which is no longer efficiently converting hydrogen sulfide.
Why the other options are wrong
- A. Engine misfires often cause a raw fuel smell or black smoke, not a rotten egg odor.
- B. Lean fuel conditions typically cause a hot, burning smell, not rotten eggs.
- D. A failing oxygen sensor can cause various performance issues but usually doesn't directly produce a rotten egg smell.
Catalytic Converter Failure
The catalytic converter's primary function is to convert harmful exhaust gases into less toxic pollutants. When it fails, it can emit a sulfurous, 'rotten egg' smell.
- Converts harmful exhaust gases
- Rotten egg smell (hydrogen sulfide) is a key symptom
- Can also cause reduced engine performance
Memory trick: Rotten eggs from the exhaust means your Cat's got a bad smell!