My 05 5.4 has developed a slight miss thast seems to be coils or plugs. My plugs only have 40,000 miles. My COPs have 140,000 miles and have never been replaced. I'm thinking of replacing all 8 of them with motorcraft OEM. How long do they normally last? It mainly happens while shifting into and out of OD at low rpms, 45-50 mph. Very random with no CEL.

 

Could be COPs but really sounds like plugs. There is no set life for COPs. They can last the life if the truck or go out at anytime. Have you cleaned the MAF and throttle body?

 

What plugs are you currently using? Use only Motorcraft spark plugs.

 

OEM plugs. They were replaced 40,000 miles ago. I need to change the fuel filter also.

Bluejay- No.

 

If you don't want to spend the money on Motorcraft cops, see if you can find some Visteons (P/N 60-1005). Another CHEAP option is Araparts (DG511 replacements), may be worth a try.

 

I'm ok spending the coin on motorcraft COPs. I think I have seen some prices aorund $180 for 8...somewhere.

 

While changing the oil, filter and fuel filter and cleaning the MAF...I removed the 2 handful of leaves under the air filter. Might help with the slight miss, or lack of air flow. ��

 

So...my miss returned and I dug into it to fix it for good. I changed the fuel filter, cleaned the MAF and the throttle body. Drove it for a few days and the miss was still present. I replaced the spark plugs with sp515. After comparing the old and new the problem was evident. Only about 50,000 miles on these and the electrodes looked pretty bad. All 8 came out fine, with the last one, #1 I think, really squeaking. I coated the shanks with anti-sieze and applied di-electric grease to the boots. Miss is fixed and hopefully my mileage improves slightly.