I have an 03 E150 code po307 which is misfire #7 cylinder and po316. Runs smooth at first when cold. Traded coils 8 for 7. Still misfire #7. Replaced injector no difference. Pulled spark plug looks like cheap autolite. There was oil around base of plug no water. Plug was not fouled or gas soaked it was clean? Any ideas please. Thanks for any ideas

 

look for a carbon trail down the side of the poselen on the plug.the spark will run down the side of the plug with a know good plug

 

you might check your o2 sensor if it was bad i dont know if it would pull up that code but it can mess with how it runs and it will make a difference if it is cold or not. also check your mass air flow sensor one of my buddys blow his engine because of a miss fire and everyone said it could not be that because it would not just mess with one but it did.

 

Make sure that the boot on the coil doesn't have a hole in it. If it does it may be arcing which will cause a misfire. Had one of those. Really hard to track down. Replace all of your plugs, boots and springs. The coils don't go bad that often.

 

I have had 3 coils go bad in the past six months

 

Changed the spark plug to platinum autolite. It worked. Thanks so much from all the advice. Jimmy

 

I have had coil problems, too. Last Tuesday she started bucking and missing. I took it to the dealer, it was the #3 coil. Under warranty less than 20k mi. This morning, less than a week later, same thing! Probably will take it in this week. I'll post when I know what the problem is.