What are common causes of spark plug fouling and typical remedy?

• A. Carbon or lead fouling from improper fuel/air mix or oil contamination; remedy is cleaning or replacing plugs, checking fuel and oil conditions, and adjusting mixture.
• B. Normal wear from aging; remedy is simply replacing with same type.
• C. Electrical insulation wear; remedy is tightening ignition coils.
• D. Water contamination in fuel; remedy is draining.

Answer: (A)

Spark plug fouling happens when deposits build up on the electrode, preventing a strong, reliable spark. The most common causes are carbon deposits from running too rich or incomplete combustion, or oil contamination that burns and leaves deposits on the plug. Lead fouling can also occur with certain fuels, leaving sticky residues on the electrodes. The typical remedy is to inspect and clean the plugs or replace them, then fix the underlying causes: verify and correct the fuel/air mixture so the engine isn’t running rich, check for oil consumption and leaks (or issues with the PCV system) and address any oil entering the combustion chamber, and ensure the ignition system and spark plug gaps are set to the manufacturer’s specifications. This approach tackles both the symptom (the fouled plug) and the root causes, reducing the chance of recurrence. Normal wear from aging, wiring or insulation issues, or fuel-contamination issues like water are different problems and won’t be resolved merely by cleaning plugs or changing seating conditions.