Verkkosigns of worn or faulty spark plugs include rough idling, difficulty starting, decreased fuel efficiency, and engine misfires. Replacing spark plugs at the. Verkkoin this spark plug guide, we cover everything from part number charts to showing you which spark plug you need for your particular model, whether that be a standard. Verkkoregular inspection and maintenance of your spark plugs can help prevent engine problems, ensure optimal performance, and extend the life of your.