Check Your 4.6L Coil-on-Plug Boots

[Scott Doughtie]

The other morning, the ST (2007) started acting sluggish and threw a CEL after a few minutes of driving. I thought it was a bad plug because of how it was acting, though I had just changed the plugs in May. Got back home and hooked up the scanner. It threw several codes for lean bank and clylinders 7 & 8 being down. I pulled the coil-on-plugs off of cylinders 7 & 8. Both plug wells were full of water. I wicked out and blew out the water. I dried the plug boots and springs. I also pulled the plugs and dried them off. I replaced everything, cranked back up with no codes. As a test, I filled a cup up with water and gently poured the water around the general area. I pulled the boots and the water was back. Lovely. Just went and bought new boots and retested with the water. No water in the plug wells.



Moral...check your CoP boots for wear and/or a poor fit/seal. I wasn't crossing rivers, but with a fair amount of rain the day before, it must have been enough for the water to get into the plug wells.

 

[Robert Caffyn]

Thanks for the heads up. If I were you, I'd start tracking down how the water got in there in the first place. Bob

 

[Steve Krusich]

I repeatedly had the same problem. The only thing that helped was spraying plug wire waterproofing on the boot. I applied several treatments.

 

[Adam Smith]

What's the best thing to put on the boots before sliding them on the plugs?

Thanks.