Replacement procedure
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Photo 1: Pull the boot
Wait for the
engine to
cool before
removing plugs.
Using a spark
plug wire puller,
grasp the boot
as far down on
the plug as possible,
twist and
pull straight
out.
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Spark plug wire puller
A spark plug wire puller makes it easy to pull the boot off.
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Photo 2: Unscrew the plug
Blow debris
away from the
spark plug recess
before removing
the spark plug.
Using the swivel
spark plug socket
and an extension,
unscrew the spark
plug.
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Swivel socket and bent handle ratchet
The right tools make removing the spark plugs simple.
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Photo 3: Gap the plugs
Gap all plugs
before installation
using the manufacturer's
specs.
Slide a gap gauge
between the center
and the side electrodes
and adjust
the electrode to
achieve a slight
drag on the gauge.
Place a small dab of
anti-seize compound
on the plug
threads and handthread
the plug into
the cylinder head.
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Gap gauge
Get the gap just right with an inexpensive gap gauge.
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Photo 4: Use the proper amount of torque
Proper spark
plug torque is
CRITICAL in today's
engines. Always
use a torque
wrench and the
manufacturer's
torque specifications!
Insufficient
torque can result in
a plug blowing
right out of the
cylinder head, taking
the threads
with it. Too much
torque distorts the
plug. If you used
anti-seize compound
on the plug
threads, reduce
torque by
10 percent.
You already know that spark
plugs wear out. Well, “burn up”
is more like it, because when a
spark jumps the gap between two electrodes,
it actually burns off (erodes)
minute amounts of metal from each one.
Over time, the gap grows to the point
where the spark can no longer make the
jump. That's when you get misfires, poor
gas mileage, lousy acceleration and, ultimately,
the dreaded “Check Engine” light.
To keep vehicles running at peak performance
for longer service intervals,
many car manufacturers install extended-life
spark plugs. Because their electrodes
are coated with precious metals that have
higher melting points, these plugs can
sometimes maintain a precise gap for up
to 100,000 miles. But even with higher
melting points, metals like yttrium (2,779
degrees F), platinum (3,222 degrees F)
and iridium (4,429 degrees F) can't stave
off erosion forever. The electrodes eventually
erode, increasing the gap, and, well,
you've already heard the rest of this story.
Replacing spark plugs
early makes sense
Unlike manufacturers' guidelines for oil
changes, which are overly cautious, the
recommendations for spark plug replacement
intervals tend to be overly optimistic.
For example, if you've already got
80,000 miles on a set of 100,000-mile
plugs, they're 80 percent worn and beginning
to take a toll
on engine performance
and gas
mileage. Worse yet, after that many miles, spark plugs
have a tendency to seize in the cylinder
head. Removing a seized plug can be a
costly job, especially if the threads in the
cylinder head are damaged in the process.
When you consider the gas mileage falloff
and the possibility of seized plugs,
early replacement makes sense.
Do it yourself
or take it to a pro?
The answer depends on the type of engine
in your vehicle. Some of the V-6 models
have very difficult spark-plug replacement
procedures that require removing portions of the intake manifold.
If you're not comfortable with that level of
disassembly, you should take your vehicle
to a pro. But if you have an engine with
easy access to the
rear bank, then
you can probably
do the job yourself. Just
be sure you gap the spark
plugs properly and use a torque
wrench.
The tools shown are available at online suppliers and auto parts stores.
