prlane

I have just purchased a 08 grand cherokee 38,400mi and the stealer/dealer said that it time for new sparkplugs 16 plugs installed for $290.00. How difficult is to change these plugs and should I stay with the factory plugs ? Is there diy page or video on this or would it be better to have the plugs change buy a good mechanic. Thanks

Bustedback

Stick with what it came from the factory with, but they are spendy, about 8 bucks a plug, so you're looking at about 130 dollars just for the plugs. I have a few vehicles with the 4.7 V8 in our fleet, and they have over 100k on the original plugs. I think you could go another 12k befor really needing to replace them unless you're have a driveability problem. The dealer may be trying to upsale you.

ol"blue

Welcome to CF. I always use what the factory/owners manual specifies, as Bustedback stated above. Read the following, it lists the part #s for the plugs, and the required gap setting. Near the bottom if you scroll down, it gives directions on how to replace the plugs for the different engines.>->http://wkjeeps.com/wk_sparkplugs.htm
We purchased out '04 WJ w/the 4.7 V8 new and we've taken it to the dealer for every thing since then, including tune-ups. I don't want to take a chance on breaking a spark plug or coil pack off in the rear while doing that job.
Good luck with your WK.

prlane

Thanks for the good info

jnicewan

The top plugs (under coils, intake side) are 30k replacement interval, the bottom plugs (under plug wires, exh side) are 100k plugs or actually 102,000 miles. The 30k plug is a yttrium enhanced copper core plug. The 100k plug is iridium tipped.

This engine calls for Bosch plugs, they are not real unique but pretty sure they are specific to 4.7's. Contrary to a lot of peoples beliefs that Bosch plugs are junk, these plugs are up there in quality. The Bosch plugs that most people would agree on being junk are the "platinum plus" lines, or the ones with the hidden center electrode.

These should be available at auto parts stores, Oreillys list them at $5.50 and $9.50 each. Or $120 for all 16 before tax LOL. The dealer probably quoted you for the top plugs only, or thats what they should have recommended.

Artful Owl

I recently purchased a 99 WJ, 4.7 - how do I get to the spark plugs ?, they seem to be covered with metal covers

Is this engine known as a 'HEMI' to you Americans ?.

gs69350

No, the 4.7 is its own deal. Overhead cam if I recall. Reminds me of the 4.6 Ford engine.

The Hemi is different. Not 100% but 5.7 is the smallest displacement I believe.

ol"blue

No,it's a DOHC, or Dual Over-Head Cam design engine.
The following info is from the Factory Service Manual:

SPARK PLUG REMOVAL
On the 4.0L 6–cylinder engine, the spark plugs are
located below the coil rail assembly. On the 4.7L V–8
engine, each individual spark plug is located under
each ignition coil. See * below(Coil removal/installation info listed below)
(1) 4.0L 6–Cylinder Engine: Prior to removing
spark plug, spray compressed air around spark plug
hole and area around spark plug. This will help prevent
foreign material from entering combustion
chamber.
(2) 4.7L V–8 Engine: Prior to removing spark plug,
spray compressed air around base of ignition coil at
cylinder head. This will help prevent foreign material
from entering combustion chamber.
(3) On the 4.0L engine the coil rail assembly must
be removed to gain access to any/all spark plug.
Refer to Ignition Coil Removal/Installation. On the
4.7L V-8 engine each individual ignition coil must be
removed to gain access to each spark plug. Refer to
Ignition Coil Removal/Installation.
(4) Remove spark plug from cylinder head using a
quality socket with a rubber or foam insert. If
equipped with a 4.7L V-8 engine, also check condition
of coil o-ring and replace as necessary.
(5) Inspect spark plug condition. Refer to Spark
Plug Conditions.

CLEANING
The plugs may be cleaned using commercially
available spark plug cleaning equipment. After cleaning,
file center electrode flat with a small point file or
jewelers file before adjusting gap.
CAUTION: Never use a motorized wire wheel brush
to clean spark plugs. Metallic deposits will remain
on spark plug insulator and will cause plug misfire.

INSTALLATION
CAUTION: The 4.7L V–8 engine is equipped with
copper core ground electrode spark plugs. They
must be replaced with the same type/number spark
plug as the original. If another spark plug is substituted,
pre-ignition will result.

Special care should be taken when installing spark
plugs into cylinder head spark plug wells. Be sure
plugs do not drop into plug wells as ground straps
may be bent resulting in a change in plug gap, or
electrodes can be damaged.
Always tighten spark plugs to specified torque.
Over tightening can cause distortion resulting in a
change in spark plug gap or a cracked porcelain insulator.
(1) Start spark plug into cylinder head by hand to
avoid cross threading.
(2) 4.0L 6–Cylinder Engine: Tighten spark plugs to
35-41 N·m (26-30 ft. lbs.) torque.
(3) 4.7L V–8 Engine: Tighten spark plugs to 27
N·m (20 ft. lbs.) torque.
(4) 4.7L V–8 Engine: Before installing coil(s),
check condition of coil o-ring and replace as necessary.
To aid in coil installation, apply silicone to coil
o-ring.
(5) Install ignition coil(s). Refer to Ignition Coil
Removal/Installation.



*IGNITION COIL
DESCRIPTION
The 4.7L V–8 engine uses 8 dedicated, and individually
fired coil (Fig. 16) for each spark plug. Each
coil is mounted directly to the top of each spark plug.

REMOVAL
An individual ignition coil is used for each spark
plug (Fig. 18). The coil fits into machined holes in the
cylinder head. A mounting stud/nut secures each coil
to the top of the intake manifold (Fig. 19). The bottom
of the coil is equipped with a rubber boot to seal
the spark plug to the coil. Inside each rubber boot is
a spring. The spring is used for a mechanical contact
between the coil and the top of the spark plug. These
rubber boots and springs are a permanent part of the
coil and are not serviced separately. An o-ring (Fig.
18) is used to seal the coil at the opening into the cylinder
head.
(1) Depending on which coil is being removed, the
throttle body air intake tube or intake box may need
to be removed to gain access to coil.
(2) Disconnect electrical connector (Fig. 19) from
coil by pushing downward on release lock on top of
connector and pull connector from coil.
(3) Clean area at base of coil with compressed air
before removal.
(4) Remove coil mounting nut from mounting stud
(Fig. 19).
(5) Carefully pull up coil from cylinder head opening
with a slight twisting action.
(6) Remove coil from vehicle.

INSTALLATION
(1) Using compressed air, blow out any dirt or contaminants
from around top of spark plug.
(2) Check condition of coil o-ring and replace as
necessary. To aid in coil installation, apply silicone to
coil o-ring.
(3) Position ignition coil into cylinder head opening
and push onto spark plug. Do this while guiding coil
base over mounting stud.
(4) Install mounting stud nut and tighten to 8 N·m
(70 in. lbs.) torque.
(5) Connect electrical connector to coil by snapping
into position.
(6) If necessary, install throttle body air tube or
box.

IGNITION COIL CAPACITOR
DESCRIPTION
Two coil capacitors are used. One of them is
located near the center of, and on the left side of the
intake manifold (Fig. 20). The other capacitor is
located near the center of, and on the right side of
the intake manifold.
OPERATION
The 2 coil capacitors are used to prevent high-voltage
spikes from interfering with the operation of certain
powertrain sensors. They are also used to help
prevent radio interference.

ol"blue

Or this might be better as it contains pics. Click images to enlarge. >->http://www.wjjeeps.com/service/sparkplugs.htm#REMOVE47

Artful Owl

It's a fair bit of work compared to my 2.5. I used to have a straight 6 Jaguar X300 and you had to through a similar procedure