My Expedition began running rough a couple of days ago, and the CEL came on. I went to Autozone to have the code checked and it coded misfire on #4. After a little research, I assumed it was the COP. I pulled the COP off of #4 to inspect it, and went ahead and switched #4 with #1 since 1 was easier to get to if I buy a new one...The truck ran great for a day (about 60 miles). This morning, the truck is running rough again. I bought a new boot for the COP (now on #1), but it didn't make a difference. Since the truck ran good for a day after I switched the 2 COPs, I need help figuring what to do next. Any advice?

 

buy a new assembly COP w/boot. replace the COP that went bad.

 

You probably jarred something on the inside when you moved it and it made an internal connection again. Probably a bad internal winding in the COP.

 

check the heater hoses running directly above the #4 cyl. they are know to leak and kill the COP. Make sure to put in some dielectric grease in the boot to keep the moisture out.

 

Thanks for the replies. Once I replace the COP I'll report back.