Flashing CEL usually indicates a misfire. If the batteries have been
disconnected recently or the keep alive memory cleared, it is possible that
a condition call "misfire profile" has not had a chance to relearn. The PCM
will need to see three closed throttle, no brake coast downs from about 50
mph to about 30 mph (from memory, here, so I may need to be forgiven) to
flag any particular cylinders.
Common on the 5.4 was for the heater hose fittings to leak on to #3 and #4,
FWIW, checking only two doesn't really indicate much. Coils can and do fail,
boots can carbon track and it's not uncommon to find moisture in one or more
spark plug wells. The boots can seal poorly enough to allow water into the
wells yet good enough to keep it from escaping.
Thanks Jim. The plugs and coils are a bear to get out so only checked the
front 2, mainly checking to see what the plugs looked like. Will check the
codes again to see if I have anything. Will also check heater hose between
#3 and #4.
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