Classic 4.6... Had that happen on my 4.6 in my '99 last year. The
coolant started to leak from the head gasket a little bit and it
gradually filled up that deep spark plug well, and the one next to it.
You don't realize it until you get that misfire code but mine seemed to
keep running fine and the code would clear, and then come back, and
clear out again. So I was trying to figure out why it was doing that.
I would see a little bit of moisture on the garage floor when it sat for
a while but it seemed clear, not anti-freeze so I thought it was from
the A/C. Anyway, as the coolant sat in that well, it ate the rubber
boot and then start arcing and I got a bad misfire one day where I had
to baby it home while towing - not fun, but luckily was only 6 miles
from home when it happened. Head gasket, two new plugs and a clean out
of the wells and it's been great. Not sure why the wells didn't boil
off and dry out on their own after the leak was stopped, but it's been
months and everything has been fine. Maybe the antifreeze prevented the
You probably need a head gasket job and have them (or you) make sure the
wells are all dried out and the wires & plugs are good while they are
there. The problem for me was that I don't use that truck much so the
problem lingered for far too long. I only put about 1K-1500K a year on
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