I apologize if I bug some purists out there, but the other Ford groups just
aren't as helpful...
Long story short, our exchange student's father has a 1999 Ford Expedition
5.4L, Eddie Bauer edition. Mechanics in his country said he needs a new
"electrical resistance" (whatever the heck that means) that goes between the
spark plug and the plug wire. I'm thinking they are confusing the clip in
the end of the plug wire that attaches to the plug with something impacting
the electrical system. I also think that these foreign mechanics don't have
a clue as I know for certain there is nothing between the plug and the
wire.... however, being this is an exported vehicle, perhaps there are some
sort of resistors put between plugs and wires. I'm not holding my breath or
taking bets on it, however.
Any insight you have is appreciated.
I think there's some missing going on and the mechanic thinks spark isn't
getting to the combustion chamber. He said there is a "coil or some manner
of electrical resistance" piece in the plug wire (they call it 'gume
tubing') that needs replacment. I say bolluks; he should check the plug and
plug wire because there may be any number of issues there, namely a faulty
plug and/or wire . However, as we're dealing with foreign techs, I am
taking nothing for granted.
What is the mileage?
I too doubt that this would be the problem unless they were messed with. I
would tend to say TUNE-UP or compression leak.
The part I would think they are talking about on the Vortec engine their is a
little short ignition wire that attaches to the coil, and in the end of this
wire is the "coiled spring" that attaches to the spark plug. these 3" wires
are replaceable or come w/new coils.
(their are 8 separate coils and ignition wires that sit on top of each of
the spark plugs)--J
Message posted via CarKB.com
Expedition 5.4L engines all use "Coil On Plug" (COP) ignition. There is an
individual coil for each plug. The coils are powered by the PCM to fire the
plugs at the correct time. First generation 5.4L Expeditions (97-02 models)
are notorious for having one or more of these coil packs fail sometime in
the first 100,000 miles. Ford issued a TSB on this subject because a large
percentage of the coils returned for diagnosis were not actually defective.
However, the Ford recommended coil diagnostic procedure is so long and
complicated, just replacing the coil is cheaper. If you have a misfire, the
PCM error code will identify the failing cylinder. The mechanics could just
replace this coil pack. It is also possible that only the spark plug has
failed. Or it is possible that the connection between the coil pack and the
spark plug has failed. Although the coil pack sits above the spark plug,
there is still a "wire" connecting them. This is generally referred to as
the spark plug boot. It can be replaced separately. It is really just a
short spark plug wire. Whenever I have my plugs replaced, I ask that all the
plug boots be replaced as well. They are relatively cheap. However, if
there is a failure, I would not just replace the boot. In order to avoid
going back to replace another part later, if I had one cylinder misfiring,
I'd replace the plug, plug boot, and coil on that cylinder. If the truck has
high mileage (more than 60,000 miles), I recommend that you replace all the
plugs and plug boots (but not the coil packs -except for the bad cylinder).
On Expeditions with 5.4L engines, it is usually one of the rear coils that
fails (#3, #4, #7, #8). They are difficult to access. I believe they fail
because of poor air flow, leading to the coil overheating, or degradation of
the plug boot. It is often claimed that a leaking heater hose over the #4
cylinder can lead to coil failure. Ford uses quick connect fitting on the
heater hoses at the firewall and sometimes they leak slightly, particularly
if they have been disconnected for some reason (like changing the spark
plugs). Your mechanic you be sure these hoses are properly attached. Many
mechanics replace the Ford quick connect fittings with a traditional clamp.
BE VERY SURE THAT WHOEVER REPLACES THE SPARK PLUGS, TORQUES THEM
PROPERLY!!!!. This is very important. If the plug are over-torqued you can
damage the heads. If the plug are under-torqued they may back out and damage
I suggest that you join the Ford Expedition Owner Mailing List. Lots of good
information from Expedition Owners is available from the members. See
I guess the idea of "Coil On Plug" ignition is to eliminate the long
run of plug wire with high voltage on it- instead they run low voltage,
high current thru the long wire, and step it up to the high voltage,
low current right at the spark plugs.
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