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I have a 2002 ford F150 with a 4.6 l v8 I bought it new in 2002 and have had good luck with it. It only has 61000 miles on it and has had no work done other than Oil changes Brakes and tires.

I really have cut down my driving in the last year since my back surgery and really havent driven it all that much I did take it on a trip to shed hunt this past spring and I got bad gas mileage Again really didnt use it all summer but I started noticing that it had a miss to it. Ihave afriend who works on cars on the side at his house and he put it on a meter and it kinda pointed towards the O2 sensors Well a few weeks ago I planned to drop it off for him to change them That very day my wife drove it to work and the truck made a loud noise and she shut it down I had a tow truck haul it to my friends and he looked it over Well it seems that a spark plug somehow blew right out of the head In doing this it also broke the coil that was attached on top of the plug Well he said the new one tightened up nicely and he replaced all the plugs and the coil (350 bucks) and I was back on the road It seemed at times to still have a small miss but not like before

Now it gets bad I think I just went out in the driveway and started it up and poom out blows the plug again Coil broken again Dang Now again this thing had never had any work done to it how did this plug loosen ??

Do you think it was ever tightened correctly at the factory?? Cant imagine the threads being good and I can see this being very expensive to repair

Thanks tt  

when was the last time you got the spark plugs changed?.... was it done professionaly?....if not spark plug threads are easily over tightend and striped....some times the head threads also strip...

there is a possibility that you can fix this with a simple heli coil....although you would have to have an odd ball spark plug.....

I've had this problem before...believe me duct tape wont work on this one...heli coil the plug back in...(cheapest thing to do)...or go back to the last person to change the plugs and show them what they did...  

This is actually a relatively common problem with 4.6L and 5.4L Ford SOHC engines.  The spark plug shaft (threaded area) is too short and can blow out even when the spark plugs were installed correclty and not overtightened.  The heli coil may work for a time but supposedly the solution below is a better way to go (or so I'm told by those more knowledgeable than I)...

http://www.timesert.com/html/sparkplugford.html