I know why those spark plugs tend to pop loose on the Ford 4.6-liter engine

Question:

Concerning the question of how to fix the problem of spark plugs popping out that was discussed in the June issue; the reader also asked if this is a common problem with the Ford 4.6-liter engine. The answer to this is YES! It’s a big-time problem with the modular Ford V-8s up through 2004.

They sometimes pop out for no reason, even if the plugs have never been changed; sometimes in as little as 20,000 miles, but most often they pop out after someone has changed spark plugs and created some thread damage.

The problem is that when those engines were built there were not enough threads provided in the head. After several years—(in 2005 if I’m remembering the year right)—Ford added a couple more turns of threads in the head to alleviate this problem.

Ford issued a service bulletin that said when replacing spark plugs, you should

use penetrating oil, then barely crack the plug loose and next let it stand for some period of time—I don’t remember the exact time but I think it was around 30 to 60 minutes. Then take the plug the rest of the way out

There probably is a way of looking up this service bulletin. If you run a web search on Ford spark plugs popping out, you will get many references to this problem.

I have a 4.6 engine in a 2003 F150 that has 90k miles on it—the spark plugs have never been changed and have not popped out. Due to all the reported problems, as long as it’s running good, I will not change the plugs no matter how many miles it has on it because of this spark plug problem.

Answer:

Thanks for your input, Dave. We are all in this hobby together, and we need to help each other whenever we can. Reader input is welcomed and appreciated.