Rather, rough idle is a symptom of another underlying issue. Our main focus here in on the Ford 6.2 spark plugs. The engine uses a whopping 16 spark plugs in total. Yes, that’s correct – two spark plugs per cylinder. It leaves a lot of room for potential misfires. Spark plugs are standard maintenance, so we don’t consider this a true problem. What happens when one spark plug is not firing? One spark plug, not firing can cause several problems. The engine may run erratically, or it may not start at all. If the problem is severe, it can damage the engine. A bad connection is the most common cause of a spark plug not firing. The spark plug may be loose, or the wire may be damaged. wrahDnl.

ford focus spark plug problems