ASE G1 Auto Maintenance and Light RepairEngine SystemsMedium
A vehicle owner reports a noticeable decrease in engine power, especially during acceleration, and the exhaust emits a strong, pungent odor similar to rotten eggs. Which of the following components is most likely failing?
- AEngine thermostat
- BEGR valve
- CCatalytic converter
- DMass air flow (MAF) sensor
Show answer & explanationAnswer & explanation
Correct answer: C. Catalytic converter
A rotten egg smell from the exhaust, combined with reduced engine power, is a classic symptom of a failing or 'plugged' catalytic converter. The sulfur smell is due to the converter failing to properly process sulfur compounds.
Why the other options are wrong
- A. A faulty thermostat would primarily affect engine operating temperature, not typically cause a rotten egg smell or significant power loss.
- B. A faulty EGR valve can cause rough idle or hesitation, but not typically a rotten egg smell or such a pronounced power loss associated with exhaust restriction.
- D. A failing MAF sensor can cause power loss and poor fuel economy, but it does not typically produce a rotten egg smell from the exhaust.
Catalytic Converter Failure
When the catalytic converter, a device that reduces toxic pollutants in exhaust gases, becomes clogged or damaged, leading to engine performance issues and distinct odors.
- Commonly causes a 'rotten egg' smell due to sulfur compounds.
- Can lead to reduced engine power and fuel efficiency.
- Often triggers a 'Check Engine' light with relevant DTCs (e.g., P0420, P0430).
Memory trick: A 'CAT' with a 'bad egg' can't 'convert' power.