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GENERALINFORMATIONAND
MAINTENANCE l-23
gap increases, the plug's voltage requirement also in-
creases. It requires a greater voltage to jump the
the spark plug counterclockwise
to loosen and re-
move the spark plug from the bore.
wider gap and about &o to three times as much volt-
age to fire the plug at high speeds than at idle. The
improved air/fuel ratio control of modern fuel injec-
tion combined with the higher voltage output of mod-
Be sure not to use a flexible extension on the
place. The click may be felt or heard, then gently pull
ern ignition systems will often allow an engine to run
socket. Use of a flexible extension may allow
back on the boot to assure proper contact.
.___.
.
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significantly longer on a set of standard spark plugs,
a shear force to be agptf' ea to me plug.
A
12. On the 3.OL fSOHC and DOHC) and 3.5L en-
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but keep in mind that efficiency will drop as the gap
shear force could break tne pug on III me
tion 3 for the installation procedure.
widens (along with fuel economy and power).
cylinder head, leading to costly and frustrat-
13. If equipped, install the center cover.
When you're removing spark plugs, work on one
ing repairs.
at a time. Don't start by removing the plug wires all at
once, because, unless you number them, they may
To install:
INSPECTION & GAPPING
11. Apply a small amount of silicone dielectric
compound to the end of the spark plug lead or inside
the spark plug boot to prevent sticking, then install
the boot to the spark plug and push until it clicks into
gines, install the upper intake manifold. Refer to Sec-
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1 the neaative bat&v cable and if
become mixed up. Take a minute before you begin
and number the wrrpc with +sne
1. Disconnect. ~~.~ --..-., -..-.-, -..-
thevehicle has been run recently, allow the engine to
thoroughly cool.
2. If equipped, remove the center cover.
3. On the 3.OL (SOHC and DOHC) and 3.5L en-
gines, the upper intake manifold must be removed to
access the rear spark plugs. Refer to Section 3 for the
removal procedure.
4. Carefully twist the spark plug wire boot to
loosen it, then pull upward and remove the boot from
the plug. Be sure to pull on the boot and not on the
wire, otherwise the connector located inside the boot
may become separated.
5. Using compressed air, blow any water or de-
bris from the spark plug well to assure that no harm-
ful contaminants are allowed to enter the combustion
chamber when the spark plug is removed. If com-
pressed air is not available, use a raa or a brush to
must be replaced.
Check the plugs for deposits and wear, If they are
7. Inspect the spark plug boot for tears or dam-
age. If.a damaged boot is found, the spark plug wire
8. Using a wire feelergauge, check and adjust
the spark plug gap. When using a gauge, the proper
size should pass between the electrodes with a slight
drag. The next larger size should not be able to pass
while the next smaller size should pass freely.
9. Carefully thread the plug into the bore by
hand. If resistance is felt before the plug is almost
completely threaded, back the plug out and begin
threading again. In small, hard to reach areas, an old
spark plug wire and boot could be used as a thread-
ing tool. The boot will hold the plug while you twist
the end of the wire and the wire is supple enough to
twist before it would allow the plug to crossthread.
Do not use the spark plug sock?
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the possibility of crossthreading and damag-
lad the plug
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by hand or using an old plug wire to prevent
ing the cylinder head bore.
10. Carefully tighten the spark plug. If the plug
you are installing is equipped with a crush washer,
seat the plug, then tighten about I/, turn to crush the
washer. If you are installing a tapered seat plug,
tighten the plug to specifications provided by the ve-
hicle or plug manufacturer.
b See Figures 98, 97, 98, 99, and 100
not going to be replaced, clean the plugs thoroughly.
Remember that any kind of deposit will decrease the
efficiency of the plug. Plugs can be cleaned on a
spark plug cleaning machine, which can sometimes
be found in service stations, or you can do an accept-
able job of cleaning with a stiff brush. If the plugs are'
cleaned, the electrodes must be filed flat. Use an ig-
nition points file, not an emery board or the like,
which will leave deposits. The electrodes must be
filed perfectly flat with sharp edges; rounded edges
reduce the spark plug voltage by as much as 50%.
Check spark plug gap before installation. The
ground electrode (the L-shaped one connected to the
body of the plug) must be parallel to the center elec-
trode and the specified size wire gauge (please refer
to the Tune-Up Specifications chart for details) must
pass between the electrodes with a slight drag:
*,NEVER adjust the gap on a used platinum
.
clean the area.
*Remove the spark plugs when the engine
is cold, if possible, to prevent damage to the
threads. If removal of the plugs is difficult,
apply a few drops of penetrating oil or sili-
cone spray to the area around the base of the
plug, and allow it a few minutes to work.
6. Using a spark plug socket that is equipped
with a rubber insert to properly hold the plug, turn
type spark plug.
Always check the gap on new plugs as they are
not always set correctly at the factory. Do not use a
flat feeler gauge when measuring the gap on a used
plug, because the reading may be inaccurate. A
round-wire type gapping tool is the best way to check
the gap. The correct gauge should pass through the
electrode gap with a slight drag. If you're in doubt, try
one size smaller and one laraer. The smaller aauqe
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