Buick Regal ongoing engine light issue with hard start, rough idle, and black exhaust fumes on Buick Regal

Some Buick Regal owners report experiencing ongoing engine light issues characterized by hard starts, rough idling, and black exhaust fumes. These problems may be indicated by the check engine light, which signals stored codes that can assist in diagnosing specific engine issues. Additionally, rough idling can stem from various factors such as vacuum leaks, spark plug problems, or ignition coil malfunctions. Hard starting may be linked to a malfunctioning IAC valve, which regulates air intake at idle, while black exhaust fumes often suggest a rich air-fuel mixture potentially caused by a faulty O2 sensor or ignition system issues. To effectively address these concerns, it is advisable for owners to check for Diagnostic Trouble Codes (DTCs), inspect ignition system components, ensure proper IAC valve function, and consider the impact of a faulty O2 sensor on engine performance.