Spark plug issues in cars can be caused by a number of factors, including worn out or dirty spark plugs, incorrect spark plug gap, over-tightened spark plugs, or a faulty ignition system. To resolve these issues, you can replace or clean the spark plugs, ensure they are correctly gapped, and check the ignition system for any faults. It is important to follow the manufacturer's recommended maintenance schedule for spark plug replacement in order to prevent issues.