I have a 01 f150 with a 4.6 in it. It ran great no problems at all. I got truck last year previous owner put new plugs and coils on it. Heater core started leaking so I just replaced that. It's all back together and now it has misfire on #6. Is there anything that it could be? Loose connection maybe or am I going to have to buy plugs and coils again

 

Swap coils to see if the msfire follows the coil. Denso or Motorcraft cops should be used. Some also say Delphi. And Motorcraft plugs.