Tried to take out a spark plug, but it doesn't move at all. I've felt no budging. Is this caused by a particular type of seizing, or is something else wrong here? Edit: it's a 2014 5.0

 

Try using an impact gun. Those few years are known for the plugs sticking, where the '98-03 were known for blowing pugs out. My son worked on the later trucks and he said to use an impact gun to take them out. If they break off, there is a tool that was made to get them out.

 

I would use some compressed air in the spark plug hole to clean out any dirt. Then I’d put some Kroil or your favorite penetrating spray/oil down in there and let it soak a while. If you start it coming out, work it out a quarter turn and back in an 1/8 of turn (and repeat as I was removing it) to allow the penetrating oil to soak all threads.

 

I have read that you want to warm up the engine a little also.

 

It's a 5.0 that has standard one piece normal plugs. It's not a 04 -08 5.4 3-V with 2-piece plugs that some are describing. Those are the ones that had the breaking issue.

 

I was referring to the battery type impact, like a 3/8 Dewalt, not an air impact. I would do as the others suggest with the blowing out and Kroil or P.B, blaster etc... then the smaller impact. You can get a lot of torque on an ratchet handle or a breaker bar, where the impact gives small bursts of power. Using a penetrant goes without saying. Use the penetrant, then drive it around for a bit, then try the rachet or the impact.

 

Kroil. Was introduced to it in the aviation industry. Love it with a capitol L. Good looking out partner!

 

I just did the plugs on my 2018 5.0 just a few days ago. I needed to add leverage with a bar on the end of a 3/8th ratchet. But that last plug on bank 2 in the back needed a 22 inch breaker bar with an added leverage bar to get that one out. Looked like whoever put the old ones in used anti-seize, which should have made it easier. Torque specs at 128 in/lb would not make it that hard to remove a plug.

 

I just did the plugs on my 2019 Lariat 5.0 and used a battery operated impact at low power.

 

Using a 1/2 breaker bar on mine gave me better control so the socket/extension part wasn't flopping around and maybe break the insulator. I avoid power tool wrenches where possible.