Cylinder Misfire | Ford Explorer Forums - Serious Explorations

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Cylinder Misfire


Well-Known Member
March 1, 2017
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City, State
Year, Model & Trim Level
2004, 4wd, 4.6l
I get our Ex back from my mother in law who has been borrowing it some this winter. Get in to drive and the Service engine light is FLASHING. Drive down the street and it is running and idling very rough. Feels like it is running on 7. Pull the codes. PO301 and PO3016. Cylinder #1 misfire and misfire detected upon start up.

Go and pull the coil pack. The previous mechanic had slathered the tip of the coil pack with some kind of clear grease. Assume to better insulate the connection. Pull the spark plug. Motorcraft plug gapped at .052. Probably 53 as I did not press too hard. Funny that the owners manual which typically is very detailed did not list any spark plug specs. Spec should be 52-56. So the plugs are good. Said to be about 35K miles old. Truck has 125k currently. Plug has some brown gunk on the outside, assume it was from the grease dripped down and getting coated with dirt.

Pull the coil pack from cylinder #5 and swap with #1. coil pack #5 was not covered in grease. Start the truck. Everything now runs fine. Smooth as butter idle. ???

I suspect that the coil pack connector had some corrosion on it. There is evidence of corrosion on the aluminum throttle body. The simple act of unplugging and plugging back in the coil pack connector was enough to get the juices flowing again. This is a fairly common issue on one of my very old cars. Does this sound about right. Either that or the coil pack is going south.

I listened to the injectors too. They all seem to be clicking along fine. Just wondering if this is the end of this issue (at least for the dry summer months) or am I going to be dealing with this again.

You may have moved things around enough to disturb some corrosion or material that had made the connection between coil and plug to be interrupted. Obviously keep track and monitor but hopefully it will continue to run like butter. If it acts up again it may be time to replace boots on all 8. The boot and spring can be removed and replaced on the coil and might be worth doing now anyway. That would be the "consumable" part of your coil over plug. Set of 8 at RockAuto should be less than $25. Easy to do and I would use a small dab of dialectric grease inside tip of new boot where contact is made with plug tip