Bob Lewis
Member
It's now October 17, 2021. I had the same question, since I changed the plugs on the wife's '07 Navigator. It uses plugs with a 9/16" wrenching flat. I'm on my '03 and it looks like these are a 5/8" plug. I'm betting the 9/16" plugs came out with the '05, VCT engines. Not sure, but a guess. Hope you survived the BS from some of the guys.Hello...quick question....what size of socket do i need to get for the*spark*plugs*in a 99 Expedition XLT 5.4L?
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