5 and 8 misfire
 

Ok so my 2007 f150 was having a massive missfire issue and I can't figure it out. It was giving codes for cylinders 5 8 and 7 missfire so first I did the plugs. All went well with that but the missfire was still there I didn't mark the original location of the coils but did do each side separately. Misfire codes stayed on for 5 and 8 but now number 6 instead of 7. So I figured it must be coils. I replaced the 3 coils and number 6 went away. Leaving numbers 5 and 8 still up. So I decided to check the injectors. I swapped numbers 5 and 8 with 6 and 7 and still keep getting the codes for 5 and 8 ???? Please help before I stick a rag down the gas cap and light it lol.

Which engine and how many miles?

A new complete set of Motorcraft plugs and coils should take care of it unless you have some bad injectors. Put some Techron in the gas. You sure you are ID'ing the cylinders correctly?

sometimes when installing the coils with the fuel rail in the way, it is easy to put the rubber boots between the spark plug and the side wall, not on the plug,so no spark to the plug! Noid lights, GM one works on fords. could be bad wiring going to the injectors too. test it.

Sorry it is the 5.4 and around 120,000 km. I know that cylinders 5678 are front to back on drivers side of engine and I did replace all spark plugs and the coils on the cylinders that are setting the codes. I can also hear the injectors pulsing so I know they are getting signal.

If they are original, the plugs on the other side are due for replacement.

Lol I replaced all 8 plugs I wouldn't just do 4 of them

Did you use Motorcraft SP-515? What brand coils did you use? Did you use dielectric grease?

I too, have a similar issue. Getting a po307. Replaced all plugs with motorcraft ones, replaced all coils and ran 2 tanks of FI cleaner. P0307 persisted so I swapped coils AND injectors around. P0307 still there. Still runs like ****.

If all else fails perform a compression test if these cyls fail then its very possible that a lash adjuster failed and collapsed allowing a follower to bounce off. Also always check the pins for the harness connection in the injectors and coil. Sometimes one or both will get bent enough to prevent a complete connection and can create a miss fire.