Ok to start, my truck is a 2007 Ford F150 5.4, the problem was that it missed under load (hard acceleration or in overdrive) the cel would flash but not stay on, so I borrowed a reader from a friend and got it to read as it was missing. The only code I could get from it was P0308 which is a misfire in cylinder 8. So I did everything I knew of to diagnose which component was the one causing the problem, moved the plug, moved the cop and moved the injector. After this I would still get the code P0308. After much searching on this site, other sites and trying numerous other fixes in vain I decided to take it to someone. But before I did I figured I would trying switching the cop and plug around again. Well I just so happened to pick cylinder 1 to swap the plug out with. When I pulled the cylinder one plug out and noticed that the tip was broke right away. I went and got a new plug, replaced it, test drove it and it had fixed the problem.

So basically my computer was trying to tell me there was a misfire in cylinder 8 (drivers side rear most cylinder, closest to steering wheel correct?) when it was actually in cylinder 1 (passenger side front most, closest to passenger side headlight correct). Has anyone heard of this before?

Maybe I'm wrong in reading where cylinder 8 is but I just wanted to post this in case anyone else is having the same problem I was.

 

I had missfire in 2,5,6. Replaced those cops, still had the problem. Repplaced the remaining cops, problem gone.

 

That's what happens when you don't disconnect the battery before touching that engine. Otherwise, this post makes no sense at all. You can screw these up if you don't know what your doing and that's the first done before you start wrenching.

 

I cant imagine swapping plugs. Just buy a new one and be done.

 

I had just changed all the plugs and cop boots maybe 1000 miles prior to all this.

 

Plus I'm in no position to just start throwing money at a problem to see what sticks. I like to figure out the problem first and then buy what I need to fix it.

 

What plugs did you use?

 

At best, the misfire codes just guide you under the hood. I had a destroyed piston and plug on cylinder 1, code was thrown for cylinder 3.

 

Motorcraft. Figured if I break any next time I change my spark plugs I already got the lisle tool I bought just in case for the first time I changed them.

 

I guess I was just being naive in thinking I could just check cylinder 8, I should have checked them all right off the bat. Lesson learned.

 

Right, but if you don't dump the KAM info, old DTC's won't go away.

 

And now it's back P0305

 

Ok, I think you just answered my question for me. originally my 05 ford 5.4 liter had a misfire on cyl 4 only when I was hard accelerating. I swapped coils from 4 to 1. Now 4 is no longer misfiring but I got a code 2 times for cyl 8 misfire and 1 code for random misfire. So what you was saying is that the swap I did as well may not be on cyl 8 but accutally on cyl 1 where I put the bad suspected coil on (easy to change later) correct?

 

I am having same exact thing happen to my 06