Hey all. I bought my eco with ~48k on it. Since then I have had the plugs changes 3 times. Each time I get less and less milage out of them before I start having mis-fires. If I have the plugs changes the truck goes back to normal. But after 10k miles if I were to stomp on it it bucks and mis-fires causing the carbon tracking and plug issues.
Any ideas if I need to look at something else? I did have 1 coil replaced previously. The truck only has 117k on it now and getting ready for my 4th plug change. Not sure if previous owner ever changed them. But it seems to fix issues at least for a little while.

 

Are you changing the lower boots too? If not, that could be part of your problem. Also, when you do, make sure you put dielectric grease on them. Otherwise you'll be doing it again and having to fish out the pieces of the old ones from down inside the plug holes. It's not fun...

 

I have paid ford to do it up to now as it's only $80. But now it's worth my time so I'll just do it. I hae paid for new boots each time but can't say 100% they actually did it.

 

Are you sure they have been gapped correctly? Someone correct me if I'm wrong, but doesn't a .028 gap work best?

 

At $80 I can pretty much guarantee that you're either a very close friend of the dealership GM or they didn't do anything. The plugs are around $40 a set and the lower boots are $35ish. It will be at least an hour of labor so add another $100 or so. A dealership should charge about $150-200 and be fair.

For a stock truck gap them to 0.030"-0.033" and be good. A hot tune could stand to be a little bit lower.