Long time lurker here. I own a 2007 F-150 XLT 5.4 Flexfuel. I was "blessed" with the plugs that crack in my truck. I had them changed probably about 4 maybe 5 years ago. I can't remember exactly right now. After doing some research even my father in law was afraid to touch them, so I knew I was better off taking it to a pro. They installed motorcraft plugs. It looks like it's time to change them out. I'm getting some serious misfires, plus it's been 100k miles since the last change, but I was told by one location that even those replacement ones crack. The place that did it originally says they haven't had a replacement one crack. Has anyone had a replacement one crack or know of instances of them cracking? I'm seriously considering doing it myself this time around because I've been to a few places and everyone wants to charge right around a grand for plugs and coils. That's seems like robbery to me. Any advice? Thanks

 

The SP515 are supposed to be the replacement plugs. They are much better than the originals and shouldn't break. Ford tech makuloco on YouTube has a few videos about it. Check them out if you haven't already. I can't remember if my SP509 plugs are marked. If your new plugs are marked with a part number, you can just pull one out and see. It's an easy job. Even if you don't down any tools, you could do it yourself for less than $200 after buying everything you need.

I wouldn't take it to a shop. I an not mechanically inclined at all and it was easy for me.

 

Original SP 507's are the problem plugs on motors with a build date before 10/09/07
The replacement plug SP 515 should come out with no problems.. SP 509 are for motors built after 10/09/07 which have the re-designed heads..

 

Thank you guys. I want to get to it this weekend. Whether is supposed to suck, so we'll see.