I have a 2005 F-150 super crew King Ranch, with about 120,000 miles on the odometer. I had the spark plugs changed and one COP replaced around 72,500 miles, which was about 6 years ago. Lately, I was getting a transmission type shudder at around 45 mph. Through some research, I found that this may be caused by a misfire from the plugs and/or COP. This morning, I did not have the transmission shudder, however, the truck started to shudder while I was stopped and the check engine light flashed. I tried to read the codes with my reader but it said there was no codes thrown? Regardless, I'm thinking that the plugs and/or COPs might be the overall cause of the problem. My question for you all is, do you think I could just replace the COP's and leave the plugs alone or should I do a wholesale change out? The plugs don't seem to have much mileage on them and I know all about the horror stories of trying to do them yourself. The COPs however look fairly straight forward of a fix. So, is it wise/prudent to just change out the COPs or should I do the wholesale change out most likely at the dealership? Thanks all.

 

I would change out the COPS and see if that fixes it, you could always take it to the dealer for a plug change later if it don't, but I think COPS will fix it. Use Motorcraft COPS.

 

Denso or Delphi cops are also acceptable.

You are getting close to 50k on the plugs, so I would probably change them.

 

Yes, it is wise to change the plugs.