I have a 2011 f150 with 5.0 engine. I was driving down the hwy and decided to pass someone and when I kicked in down at 75 and and reached about 85, the rpm's close to 4,000, the engine light started flashing I could feel a miss and as the truck kept getting slower and slower, after about a mile, the light stopped flashing and the miss went away. Scanning revealed codes po300, p0301 and p0302. To make a long story short, I have replaced the 1,2 plugs, coils and injectors and it still produces the same misfire every time I put it under the same conditions @80-85 and it still smooths out with in a mile or so after I level the speed.
I have been working on fords since the 70's and I am dealer certified but I don't work at a dealer anymore. It feels like the lifter pump up on these two cylinders at high rpm's and then bleed down after I slow down. I can almost tell you when it's about to smooth out during this time.

Any ideas?

 

i can't recall the configuration of this engine.... haven't had my 11 in about 5 years. However, are there any coolant hoses/fittings over top of any of the coils? This was an issue in older models. I had a 99 5.4 that would leak coolant into the #4 coil i think, which would cause it to short out under heave acceleration. If you have not already done so, you could try to remove all coils and blow out the plug pockets with air, then go on another test run.

You can also swap a couple of coils around, and see if you can throw a code on a new cylinder.... perhaps one (or both) of the coils you just installed is new, but bad? It is very frustrating when this happens, but i have seen it more times than i can count!

Lastly, not questioning your abilities, but are you sure you have the correct cylinders for #1 and #2? Those should be the front two on the passenger side of the block.

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