solpushcart

I replaced my spark plugs last weekend. I have 261k miles in this 2007 5.4. It ran great before the change, but the plugs had about 55k miles on them. These are the 7th set that went in. Coils were replaced last year when I had 1 fail.
Now, after all said and done, I have a slight stutter in the idle. I was thinking I might not have gotten 1 of the coils all the way on. Does anyone have a secret to figure which one it might be? I would hate to spend another 2 1/2 hours tearing everything off to check them all. Especially when it's like 115 degrees.

nrivera04

Why so many sets of plugs?

My guess would be one of the new plugs was already broke or cracked on install.

techrep

iTrader: (1)

I'm thinking he is not using Motorcraft plugs. Did you ever replace the boots and springs and did you apply some Dielectric grease to the boot ends ??

SCORGE

That's like 40k per set. What brand plugs and COPS are you using?
EDIT: I've had cheap ebay coils in for almost 2 years without issue, but I bought some from a big box auto store one time and had two fail within 6 months

solpushcart

I replace them soon as to hopefully never have to deal with broken ones. Both plugs and coils are OEM Motorcraft.

nrivera04

As long as you're installed SP515's broke plugs shouldn't be much of an issue. Assuming you had new boots on the coils, I'm still saying broke plug. You said your problem didn't show up until you changed plugs... What else could it be?

techrep

iTrader: (1)

Yeah. Could have a cracked plug ..