* Catalytic Converter Issues: A failing catalytic converter is a primary suspect. The converter is designed to break down harmful emissions, including sulfur compounds. If it's damaged or clogged, these compounds can pass through unprocessed, resulting in a sulfur smell. A rough idle often accompanies a failing catalytic converter, as it restricts exhaust flow.
* Fuel Injector Problems: Malfunctioning fuel injectors can lead to incomplete combustion. If an injector is clogged or delivering an incorrect fuel/air mixture, some fuel might not burn completely, releasing sulfur compounds into the exhaust. A rough idle is a classic symptom of injector issues.
* Ignition System Problems: Problems with spark plugs, ignition coils, or the distributor (in older vehicles) can cause incomplete combustion, leading to unburnt fuel and the sulfur smell. A rough idle is also common with ignition issues.
* Air/Fuel Mixture Problems: An incorrect air/fuel mixture, often due to a faulty oxygen sensor or mass airflow sensor, can result in incomplete combustion and the sulfur smell. A rough idle frequently accompanies such problems.
* Exhaust Leak: While less likely to directly *cause* the sulfur smell, an exhaust leak *before* the catalytic converter can allow unburnt fuel and sulfur compounds to escape, intensifying the smell. An exhaust leak can also contribute to a rough idle.
* Low-Quality Fuel: While less likely to cause a rough idle on its own, using fuel with a high sulfur content can exacerbate the smell if other combustion problems are present.
Important Note: A strong sulfur smell from the exhaust is a serious issue. It indicates incomplete combustion, which can lead to increased emissions and potential engine damage. You should have your vehicle inspected by a qualified mechanic as soon as possible to diagnose and repair the underlying problem.
