Q: What could be causing a rotten egg smell to come out of my car’s tailpipe?
A: The smell is from a sulfur buildup in the catalytic converter. The converter or other emission system component may be faulty. If the check engine light has come on, a diagnostic code is triggered and stored in the car’s computer. A service technician can retrieve the code with a scan tool. Sometimes you can get a tank of gas that has a high sulfur content. Try filling up with a different brand of gasoline. If this doesn’t work, a repair facility may be able to diagnose the problem further by using an exhaust gas analyzer.