A bad EVAP (Evaporative Emission Control) canister may cause a wide range of symptoms. The most common symptom is the check engine light coming on, as this indicates that there has been an issue with the vehicle's evaporative emission control system. Other signs include poor fuel economy, rough idle, misfires and stalling - all of which are caused by excess fuel vapors not being burned off in the combustion chamber. Additionally, you may notice a sulfur-like smell when starting your car or while driving due to the gas fumes leaking from the canister. If any of these symptoms seem familiar to you it’s important to get your vehicle checked out right away as a malfunctioning EVAP canister could lead to further damage if left unchecked for too long.