doing my second set of plugs 180000km, doing this i have been replacing the boots too, then noticed hair line cracks on the tops of my COP on the 4 on the drivers side. Do I have to replace? Id rather not they are expen$ive at 50/per. Thoughts? I was thinking of doing plugs and see if the truck runs better with just plugs and boots. I know nothing about COP'S.

 

Depends on if the cracks are deep to where the COP will contract and expand when subjected to the heat and cold...any mis-fire’s going on ?? if mine had crack’s I would replace...you can always buy a set of Accel COP’s and try that out...

 

just an update , did all plugs and inspected all coils , cleaned them up good, FORD service guy said if you spray water on the coils runnung and have no arking, they are probally good. I put some epoxy on the coils to seal them and in they went, new plugs fixed my problem of studdering and mialage. FYI on my 3rd set of plugs at 180000km.