Hello!!
I was looking into doing a spark plug change here soon, and was wandering when the COP's need to be replace?

I've read how people have changed them with the plugs, but my truck only has 50k on it.

I'm looking at the E3 plugs for my 2006 5.4.

 

I think the owners manual says either check or replace at 100k, but imo if there is nothing wrong with the ones you got, leave em alone.

 

Maybe it was too late but, i changed my stock ones out when the cel threw a cylinder misfire code at around 285,000 mi.

 

There is no recommended time/mileage interval. You change them when they start to misfire.

 

Out in the middle of nowhere..... j/k

 

You will get a warning - it will start with a low grade misfire. It will start to shudder right after it shifts into OD and the torque converter locks up at light loads - generally in the 40 to 50 mph range. Giving it more gas will smooth it out.