I have a 1994 F-150 with 4.9 liter straight 6 that we are having some difficulty with. While attempting to remove the spark plugs we found that the plugs break loose easily but they come out about 2 full turns and then become tight in the head. They are not cross threaded or stripped and none of us has ever experienced this before. We did not want to use excessive force so we simply tightened them back down and the engine runs fine. They turn freely and can even be turned with fingers about 2 full turns counterclockwise before they bind up. Any advice or help will be greatly appreciated. We don't want to break anything.

 

spray some wd-40 in there let it sit for about 10min then give it a try.

 

X2. You know you didn't cross thread them! Anyway, you don't have much of a choice, sooner or later they have to come out. I would suggest getting some of that spark plug anti seize paste for the replacement plugs & say a prayer! Install the plugs to spec pressure if you have a torque wrench laying around. No use pushin your luck!