I checked my plugs today and they all looked the same. They were pretty good for having 35000 miles on them. The two middle plugs were around .036 and the other 4 were all a little more than .040. I set them all to .034. After I was done I took the truck out to see if there were any changes and the missing between 50 & 60 is worse. Acceleration seems to be better though. Any thoughts?

 

Take all your plugs out and put them in the drier, tumble low for 15 minutes. Then put them back in your truck. This seems to be how Ford gaps their plugs at the factory.

 

Were the plugs really tight when removing? If so you may have developed a hair-line crack on at least one of them. Also, how tight did you re-install the plugs? I believe the torque spec is 133 in/lbs for the spark plugs which is just little tighter than hand tight. If you went tighter than that, you may have cracked a plug.

 

I think if the plugs were cracked the truck wouldn't run right at all.

 

Maybe, maybe not. I've seen where it will idle good but under load (especially with boost) is where you'll notice for sure.

 

I probably did, I didn't use a torque wrench so they are in close to 15 ftlbs. That would be a few pounds over your spec. All of the passenger side plugs were very tight. I think I'll be buying a new set today gap them a bit wider and see what happens. I noticed a few plugs had what looked like rust on the insulator right at where it meets metal. I haven't seen that on automotive engines before.

 

I wouldn't go any wider with the gap. The new for '13 spec is .030" to .033" so I'd go with that.

 

I put in NGK 6509's and closed the gap down to .033. The truck does accelerate better like before. I think my miss/shudder getting worse yesterday had to do with the weather and not with the plugs because it's still there. I also noticed that the factory plugs are NGK's.
On to the next idea.

 

Bad fuel?

 

Naw, the temperature dropped 30 degrees yesterday. I've been on the same tank all week.