I've got a 04 f150 with a 4.6 v8. It's my work truck. 130k miles. When I bought it, I thought it idled rough, but the dealer said I just wasn't used to a v8. My prior truck was a v6. Never had a problem with the truck from day 1, maybe on wet days it runs weird when I start it up for a minute. Today after work, I stopped across the highway at Kmart for cat food. I was in and out real quick. I started the truck up and there was a loud BANG! After which the engine was running bad, like it was missing one or two cylinders. I limped back across the highway to the shop and did a quickie inspection. It was obviously missing on a cylinder or two, not leaking anything, and nothing was visibly wrong. So I started pulling plugs from the passenger side where it was making the noise. The plugs are toast, barely any metal left on top and they're all really loose. I get to the 3rd plug back and the plug, wire and boot all come out together. The coil on top of the plug is cracked in two. My theory is when I started the engine it blew the plug out of the cylinder. They were all loose on that side, the one that blew must have worked its way out and finally the compression from the cylinder blew it out of the hole. I ran to Murray's and got new plugs and a new coil for the one that was busted. Plugged them in, started the engine up and it ran smooooooth. Probably smoother than it originally did. It always had a rough idle. I'm thinking those plugs were never torqued down and worked their way loose over time. The truck runs really well after the change. I thought for sure I blew a rod or threw a piston. I'm glad it was such a minor problem. Don't have the $$ to replace a truck right now, especially a work truck. I'm glad it didn't happen when I was loaded up and pulling the trailer. No way I would have made it back. Any thoughts or theories about why the piston blew out?
I don't remember if the 4.6 was one of them, but I know there are some Ford V8s that had an issue with the spark plug threads in the head being very thin. The thin amount of metal is prone to failure/stripping out. There are special tool kits for repairing the threads in these engines. You may want to check your threads in the hole that shot the plug out.
I had been told the opposite by a guy that worked for Ford. That they were having problems with the v8 engines at the 100k mile tune up. The plugs were getting stuck in the heads and breaking off, so that they had to be drilled out.
Ive got a 4.6 in my Explorer, so I follow the http://www.explorerforum.com/ forum just as much as this one :laugh: Anyway, it is a know problem with the 4.6 that they will spit plugs Ive been lucky so far with 85k showing. My father had a couple spit out a few months ago. Rips the treads out of the hole too. It can be fixed on the truck, cost dad $175 for 2 plugs to be tapped, add an insert, and plug installed again. It cost so much because of the special tools required to do it on the truck instead of removing the head. Search that site for spitting plugs and you'll get lots that know from experience.
I also must add that it seems its mostly 03 and older that it happens too, apparently there was a aluminum composition change for the aluminum heads around 04... but not unheard of in 04+
If you were able to make'em tight, Id say you're in the clear:beers2: When dads blew out, there was nothing left to put them back in to. He thought "huh, plug must have been loose" and went to put them back in and discovered there were no treads left
I don't know anything at all about these engines but if it were me I would be checking the plugs from time to time.
If the truck has 3 valves per cylinder then the plugs will be hard to remove from carbon on the bottom of the plugs, and the plug socket will be a 9/16, If the truck is not 3 valves then the problem will be the plugs blowing out of the head and taking the threads with them. Also it will have a 5/8 head. Any good machine shop will be able to rethread the damaged cylinders while still on the truck, it is a tricky job, at my shop the guy will come and do it for $100 per cyl. Hope this helps. Bill.
