Ford Misfire

This F150 had a misfire I could feel with the engine running. It felt like a secondary ignition problem. It's hard to describe. I've heard it called "fishbite". Sort of miss miss hit miss. Very random and intermittent at low rpms. Anyway.....

The stored codes showed #2 cylinder had been misfiring.

It's important to note that a misfire code only means there was a misfire. The code doesn't tell you why it was missing. Ignition misfires are the most common on a Ford and it did feel like an ignition misfire. The most helpful item here is that we can start focusing on #2 cylinder without having to determine on our own which cylinder has the misfire. Another useful check is called mode 6. If we pull up mode 6 on the scan tool we can look at the other cylinders for any misfires that the engine computer noticed but weren't bad enough to set codes. Only #2 had misfire counts stored.

Time to take a look at #2 spark plug. It's hard to see in the picture but there was a lot of moisture (water) on the plug boot and even more on the spark plug itself. 

The spark would go wild in that moisture. There is our misfire. A new plug and a new coil is needed for this cylinder. The other cylinders had no moisture but got new plugs as well. The plug boot on #7 was in bad shape and was replaced.

Thanks for reading!

Kenneth Hayes

G&G Auto Repair