Hello I have an with my truck 03 5.4l the miss only shows up when it's warmed up and when I'm accelerating though it just started yesterday morning and on my way home a code poped up saying cylinder 6 miss fire. But it's completely fine idling. If I Rev it in park or neutral there's no miss either only when there is a load on the engine any ideas

 

What's the code? Okay at idle + Cy 6 misfire = bad coil I'm almost 90% willing to bet, swap coil #6 with 5 or what ever is easiest and see if you throw a misfire on that cylinder. If so easy fix! Use TRT30 online at advance and save like 10$ on a MOTORCRAFT coil. Trust me you want true OE coils, report back!

 

It's fine at idle and it's fine If I Rev it in neutral or park but as soon as I give it some gas in drive or reverse it starts missing

 

I know we've established that, my diagnosis still stands the same, do you have the ability to pull the code? Run up to your local auto parts store and have them read the DTCs and give is a P code

 

P0306 I've erased it twice same code each time

 

Have you swapped #6 coil with another? Do that it'll take literally 15minuts, 7 if you know what your doing.

Steps

1) unclip electrical connector from coil
2) remove bolt from coil
3) pull coil
4) swap coils around drive like you did to throw a code, if it throws a misfire code for the one you swapped you know you have a bad coil


When were the plugs last changed?

Chances are you havnt fouled a plug so your most likely good their you'd really have to drive with that misfire for a good little bit. Report back with results, nothing more we can do from this side of the Internet.

 

Bad coil, classic.
Bet it only happens at certain speed/rpm range too.
Swap coil to confirm.

 

I was trying to say that for the past 3 posts lol