06 mountaineer misfire under load P0300, 302, 306 & 307

[breezstorm]

I am working on a 2006 Mercury Mountaineer V8 3V. About 6 months ago had P0300 (random misfire) and a code for the number 7 coil. I replaced all the plugs and the 1 coil and the car ran great. About 3 wks ago the car started missing again. I scanned it and it came up with P0300, 302, 306 and 307. I checked all the plugs and swapped out the coils for good measure and it is still running poorly. The check engine light is always on. The car doesn't misfire at idle or under normal load. Under heavy acceleration it does misfire and going up a hill it misfires and the light blinks. There are no other codes in the system and the freeze frame data didn't point out any obvious problems. Any suggestions..?

 

[Birdy]

My first guess would be those plugs. Did you see any brownish marks at the bottom of the porcelain? Iv'e been having more and more problems with platinum plugs of every brand, even fairly new ones, they arc through the bottom of the porcelain and miss under load like you're saying.