ASE G1 Auto Maintenance and Light RepairEngine SystemsMedium
A vehicle owner reports a noticeable decrease in fuel economy and a strong, unpleasant odor from the exhaust, often described as 'rotten eggs'. The check engine light is illuminated. Which component is most likely failing?
- AEngine coolant temperature (ECT) sensor
- BMass airflow (MAF) sensor
- CCatalytic converter
- DEGR valve
Show answer & explanationAnswer & explanation
Correct answer: C. Catalytic converter
A 'rotten egg' smell from the exhaust, combined with decreased fuel economy and a check engine light, are classic symptoms of a failing catalytic converter that is no longer efficiently converting hydrogen sulfide into odorless compounds.
Why the other options are wrong
- A. A failing ECT sensor affects fuel enrichment and could cause poor fuel economy, but not a rotten egg smell.
- B. A faulty MAF sensor affects air-fuel mixture, causing performance issues and poor fuel economy, but not typically a rotten egg smell.
- D. A failing EGR valve typically causes rough idle, hesitation, or pinging, not a rotten egg smell.
Catalytic Converter Failure Signs
Signs of a failing catalytic converter include a 'rotten egg' smell from the exhaust, reduced engine performance, decreased fuel efficiency, and an illuminated Check Engine Light.
- Converts harmful exhaust gases.
- Sulfur smell is a key indicator of failure.
- Can cause power loss and fuel economy issues.
Memory trick: Rotten eggs mean the cat's gone bad.