Oil Fouled Plug How to Troubleshoot | Ford Explorer Forums - Serious Explorations

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Oil Fouled Plug How to Troubleshoot

alohamonte

Well-Known Member
Joined
October 4, 2007
Messages
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City, State
Glendale, AZ
Year, Model & Trim Level
1998 Explorer 4.0 4x4
Looking for the procedure to troubleshoot an oil fouled spark plug. I believe it's #4 plug (drivers side front, closest to the radiator).

I found this when changing all plugs today as part of a tuneup. The others all had a bit of dry carbon on the threads.

No CEL but I did feel an intermittent hesitation prior to the work. Running the oem Motorcraft Platinum Finewire. Also replaced the wires and coil pack.

Starts up and runs great now.

Thanks
 






if the oil was only found on the treads of the plug (and not the tip) you probably have a leaky valve cover. no big deal. if there was oil fouling on the tip of the plug, you're looking at either a leaky valve seal or worn piston rings/cylinder walls.
 






It was wet on just the threads.

I research the valve cover bit more and looks like a plugged oil drainback hole at the top of the cylinder head can definitely cause this situation.

While the valve covers are off (first time in 180,000 miles) should I do any other recommended preventive maintenance?
 












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