Originally Posted by
Jeff Monson
The problem with the design of the plug is it extends down into the cylinder too far and becomes covered in carbon. When you try to remove the plug, it snaps off the bottom portion that is built up with carbon. Once that happens you must break out the porcelian, tap interioir threads into the broken portion so you can attach a slide hammer to extract the culprit.
We do alot of tune ups on these models and warn the customer of the possible outcome. I'd say 1 out of 15 plugs will break. Not as bad as they make it out to be. I have never had to remove a cylinder head yet. If care is taken to make sure the engine is completely cold, and be care is taken when loosening the plug, you will have better success.
Its not the best design in the world, but its a 100k plug also. To me the reliability of the F150 and lack of common failures outweighs the spark plug issue. I'm sure there are owners that have spent the "several thousands" on a tune up that will disagree.