Toyota Corolla spark plug issue with excessive soot buildup on Toyota Corolla

Some Toyota Corolla owners report experiencing excessive soot buildup on spark plugs, which can lead to misfires by insulating the electrode and preventing a proper electrical connection. Symptoms of bad spark plugs include poor acceleration, rough idle, engine misfires, poor fuel economy, an illuminated check engine light, engine knocking noises, and sometimes hard starting. Additionally, faulty valve stem seals may cause oil pooling in the combustion chamber, quickly fouling the plugs; regular cleaning every 5,000 miles is recommended to mitigate this issue. Signs of a fouled spark plug include being covered in oil or soot, having melted or excessively eroded tops, or cracks in the housing. During tune-ups aimed at improving fuel economy, checking the spark plugs is common, as misfiring is a prevalent symptom of bad plugs. Engine misfiring can result in uneven running, stuttering during acceleration, and inconsistent power while driving. To verify the condition of the spark plug, some owners use a spark plug tester to check for a blue or orange/red arc, indicating proper function or potential ignition system issues. Addressing these concerns is crucial for maintaining optimal engine performance and preventing further complications.