Ford 3 valve 4.6L & 5.4L intermittent miss

[BBR]

Wifey's 2007 Mountaineer developed a intermittent miss with no check engine light. Pulled a coil pack and the plug boot looked like this.



I pulled all the coil pack/plug boots and squirted in some dielectric grease (available at auto parts stores). Reinstalled and the miss was cured. I just wonder how many coil packs have been replaced all because of a little continuity or ozone buildup problem? haha

[milner351]

I was hoping you weren't going to show us pictures of spark plugs that had most of the head threads still attached....

[BBR]

No, but I bet plenty of plugs and coil packs have been replaced trying to fix this!!

[Bamfster]

Man oh man .... the 3 valve 5.4! If I never see one again it'll be too soon.

IMHO, I wouldn't rely on it being just the plug boots .... the last one I had in with an intermittent miss turned out to be the early stages of cam phaser failure.

I hope that was all it was James.

[BBR]

Me too.

We had 2 5.4L 3 valve trucks at work. We replaced coil packs on one of then a couple of times chasing this kind of an issue. Wish I would have known about this then.

[TheSilverBuick]

There shouldn't be any o-zone in the spark plug hole until after it's already missing, aka the arc going to the head. There is probably a few cracks or holes in the insulation already and the di-electric grease will only temporarily patch it IMO. It probably needs a new coil pack because the boot insulation is bad. Good news is they must fail so often that new ones practically go for the price of a spark plug on E-bay.

[BBR]

Still running smooth. In fact, it is so smooth there have been 2 times where I had to look at the tach to make sure it was actually running. Almost hit the key to try to start it when it was already running.

[Beagle]

I'm thinking about pulling the 150k mile plugs from the 351. It's feeling like it has a cam at idle. haha. I love this new stuff! Dielectric grease, when called by name, might scare the "old guy" at O'Reilly that you know what it is, and what it works good for. I'm all for scaring the "old guy"... lol.

Good call.

[ls7gto]

at the dealership, you can do a coil stress test, to test the coils. You can see the wave form to know if the coil is going bad. And Ford sells a great Dielectric grease, that is also a caliper slide lube!

[BBR]

Still running smooth as a baby's butt. Wife took it on a trip last week and it has been doing great.

I got my grease at OReilly. Something like $2.50 for a tube.