My 98 4.6 has 116000km or 73000 mile.The manual says to replace the plugs at 100000km or 63000 miles.Why is there a difference between the U.S and Canadian manuals?I stopped by the stealership to get the price for the service.First they wanted $400 then $200 since my truck has wires instead of cops.I almost fainted.Then is asked about torque specs and if were going to let it sit in the shop over night so the motor would be cold.I got a look like i was from another planet.
If i had not asked about the cops i would have been charged double price so they could damage the threads on the headsThis is a blue oval dealership.
Now i trust no one to work on this motor.Should i change them out now at 73000 miles or wait.Should i take it to the stealership and who pays if they screw it up.I could do it myself but how can you trust the torque wrench to be at spec when you have two extentions with a universal.I'm an industrial electrician and a refrigeration mechanic and i have never seen equipment designed to fail durring/because of a service procedure like this.

 

I normally change plugs in my vehicles at around 50-60K miles. I don't believe that any spark plug, regardless of construction, will maintain full effiency up to 100K miles.

 

Matt,

Do them yourself. Your torque wrench will be accurate enough and you won't have to worry about those idiots screwing up your truck.

Sounds like you fix things for a living. You will do fine trusting your own skills.

Steve

 

You can do this yourself without a torque wrench. I'm not sure what style plug is used on that 4.6 but here are general rules when installing plugs. If it uses a gasket style plug when it contacts the head you want to give it 1/4 to as much as 1/2 turn (usually somewhere in between). This allows the gasket to crush down and form a seal. You'll feel it when it's tight enough. A tapered plug will need no more then 1/8 turn once it contacts the head, make sure to put anti seize on the threads to make future removal easier and prevent any damage to the threads. Once you do a couple you will develop a feel for it and know when it's installed properly.