P0304, then P0304 and P0306 Codes

[b3ross]

Hey Guys I have a 99 ranger with a V6 4.0 (114,000 miles), yesterday the truck started running horrible and the Check Engine light finally came on, with the P0304 code, so i replaced all plugs and wires, the lady at Advanced Auto sold me Autolite XP (extreme performance) plugs. Truck ran great following, then today less then 24 hrs later the same thing happened on the freeway, took the truck back to autozone and they pulled P0304 and P0306 mis-firing codes. replaced coil, still same problem, then took out the plugs and they were almost white because of how hott they were running, then replaced all plugs with motocraft about 5 hrs ago, trucks running good, Any Ideas ? Advance Auto sell me the wrong plugs the first time?

 

[Runnin'OnEmpty]

Hey Guys I have a 99 ranger with a V6 4.0 (114,000 miles), yesterday the truck started running horrible and the Check Engine light finally came on, with the P0304 code, so i replaced all plugs and wires, the lady at Advanced Auto sold me Autolite XP (extreme performance) plugs. Truck ran great following, then today less then 24 hrs later the same thing happened on the freeway, took the truck back to autozone and they pulled P0304 and P0306 mis-firing codes. replaced coil, still same problem, then took out the plugs and they were almost white because of how hott they were running, then replaced all plugs with motocraft about 5 hrs ago, trucks running good, Any Ideas ? Advance Auto sell me the wrong plugs the first time?

I was going to suggest changing the coil pack, but you already did that.....
The only thing that is common to #4 cyl and #6 cyl is the placement of their terminals on the coil pack. They're right next to each other, so there's a chance of sparking between the two terminals on the coil pack.

Make sure the #4 and #6 wires aren't placed right next to each other where they're routed to the plugs.

Also try cleaning the plug-in for the coil pack. Could be a cross-firing situation there.....