Ever since I completed a repair on a blown out spark plug on my 4.6, its running like its got a cylinder out. I check and listen under the hood and while it sounds like an exhaust leak, it still runs really bad......like its only running on 7 cylinders. Have I done something wrong? Did the repair kit, from NAPA, fail already? Some help on this would be much appreciated.

 

The only repair kit that works well is a Timesert. Check all the rest of the plugs for 28 ft/lb torque.

 

Well, hard to say. The ticking exhuast leak sound is a tell tale sign of a spark plug getting ready to let go. Could be a bad repair on the one you did or could be an additional one on its way out. Check all the plugs to insure they're installed/torqued properly. If you find one loose, that may be the sound culprit. As for the repair; there's only one dependable, permanent repair out there (well, two actually, but one of them is pretty cost prohibitive) and that's a TimeSert. Don't know anything about the NAPA kit but can only assume it's similar to a heli-coil in some fashion.

 

Did you replace the COP on the blown plug? If not, it may be damaged.

 

compression test the affected cylinder. Its possible in the blow out or repair process debris came loose in there and damaged a valve..

 

Something to consider about the repair process, that I seldom see addressed, is spark plug ground with an insert in place. I see kit manufacturers that recommend hi-temp black/sensor safe silicone to help lock the insert in place....others, its just red lok tite (only good to 300*f btw, the hi-temp red goes to 400*f). One would think that with the number of threads making contact between the insert and head, and plug to insert, that surely a decent ground exists, even with silicone or lok tite in use.

I'm basically bringing this up because I *have* seen poor grounds before when sealers, lok tite, etc has been used, resulting in a very annoying intermittent miss (literally wanted to shoot that truck). This can also have an effect on heat transfer from the plug to the head as I understand it after hours and hours of reading up on this wonderful subject. Also, while the difference should be negligible, I've read inserts can result in plugs overheating, especially if you're running a hotter plug to start with.

Anyway, if you're still battling the 7 cylinder blues, its something you might consider checking. I'd try a bit of dielectric grease on the threads of a new plug and see if it lights or not. You might use it on the coil and injector connections as well, certainly worth a try.... I personally use that stuff on ANY electrical connection I find suspect, or just want to reinforce. Its certainly cheap insurance. I also agree with previous replies that you run a compression check on that cylinder, and I'd even take a peek inside with an inspection camera if you have access to one.

Good luck, and I hope you've already got it fixed, but maybe this will help turn on a light bulb for someone else in the future. I'm off to ream and tap some new threads on my F2Fiddy myself (far back, right side, grumble grumble). I just finished fabricating an insert installation tool that guarantees they'll stay exactly where i set em, and won't back out with the tool upon removal. Nothing like new tool test drives.....especially when no one else has one :-P