Rotten Egg Smell When Accelerating
A rotten egg (sulfur) smell during acceleration in a 2019 Honda Civic typically indicates a failing catalytic converter or an overly rich fuel mixture causing the converter to overheat and emit hydrogen sulfide.
Diagnosis Details
Possible Causes
Failing catalytic converter – internal substrate is contaminated or damaged, causing sulfur compounds to be released as hydrogen sulfide.
Rich fuel mixture – faulty oxygen sensor, fuel injector leak, or engine misfire can cause unburned fuel to overload the catalytic converter.
Contaminated fuel – high sulfur content in gasoline can produce the smell, especially if the tank was filled with low-quality fuel.
Related OBD-II Codes
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What You Should Do
Check for diagnostic trouble codes (DTCs) using an OBD-II scanner.
Inspect the catalytic converter for physical damage or overheating.
Test oxygen sensor readings and fuel trim values.
If codes like P0420 are present, the catalytic converter likely needs replacement.
Also verify fuel quality and consider using a fuel system cleaner.
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Disclaimer: This AI-generated diagnosis is for informational reference only. Always consult a qualified mechanic for an in-person inspection. AutOwner is not responsible for decisions made based on this information.
