Last month I got a P0308 code. Replaced the COP (not the spark plug) and it fixed the problem. I had read the service bulletin and it scared me into not changing the plug, especially since the COP cleared up the issue.

A few days ago I got a P0307 code and I could definitely feel the 'miss' (intermitantly). I replaced the COP and spark plug (the dealer had to extract the broken plug). It fixed the problem (for less than an hour).

On my way home, I got a P0306 code and there is a definite 'miss' (intermitantly).

I haven't done anything yet because I'm wandering if there is something I'm missing. Is there some way these problems could be related? It seems awefully coincidental.

Do I change the COP and plug on #6 or what? What would you do?

Thank you,
David
Gadsden, AL
Ford F-250 Super Duty, Crew cab, 4x4, 5.4 liter, Gas, 115k miles

(PS I do feel more comfortable changing the plugs, since I see what the problem is in the design. I didn't exactly follow the bulletin when I broke the plug off. I didn't allow it to soak for 2 hours.)

 

Was the truck tuned up at 100k miles?

If not, change the plugs. If so, what plugs did you use?

 

@redford- I didn't change them at 100,000. I've replaced two plugs, as of today, with Autolite HT1. I've replaced 3 COP to date, with BWD. The parts have all come from Advance Auto.

Previously I've been afraid to attempt the plug exchange but if I understand it right, any carbon buildup will only get worse. Would you change the coils as well?

Thank you,
David

 

And now... there is a P0174 code. What's happening?
David

 

You could have a dirty or faulty MAF sensor. Clean MAF with MAF cleaner, pull the ground off the battery for a minute to let the truck re-learn. See if that fixes it.

Or, you might have a vacuum leak. Check PCV valve hose and other hoses for leaks.