2007 ISUZU KB P190 engine

Engine Management – V6 – Service Operations Page 6C1-3–48

2.22 Spark Plugs
Service Precautions
1 Allow the engine to cool (to at least 50°C) before attempting to remove spark plugs. Attempting to remove spark
plugs from a hot engine may cause the plug / cylinder head threads to bind, resulting in tearing of the alloy cylinder
head threads.
2 Clean the spark plug recess area before removing any spark plug. Failure to do so could result in engine damage because of dirt or other foreign material entering the cylinder head or by the contamination of the cylinder head
threads. The contaminated threads may then prevent the correct seating of the new or replaced plug. If required,
use a thread chaser to clean the threads of any contamination where this is suspected.
3 Under no circumstances should the spark plug/s gap be adjusted. If the gap is not within specifications,
replace the spark plug.
Figure 6C1-3 – 66
Remove
1 Turn the ignition switch off.
2 Remove the ignition coil/s, refer to 2.15 Ignition Coil.
3 Using a suitable spark plug socket, loosen the spark plug slightly and then re-tighten to break away any carbon deposits on the threads.

Wear eye protection to avoid injury.
4 Loosen the spark plug once again one or two turns, then use compressed air to remove any foreign material that may otherwise enter the combustion chamber.
5 Remove the spark plug (1).
6 Repeat as required for the remaining spark plugs.
NOTE
Place each spark plug in the same order as that
of removal. This will enable any abnormal spark
plug condition to be identified with the cylinder.
NOTE
If the spark plugs are removed for an indefinite
period before installation, plug the spark plug
openings to prevent foreign particle ingress.
7 Repeat steps 2 to 5 for the remaining spark plugs as required.
Figure 6C1-3 – 67
Inspect
The spark plugs must not be re-gapped. If the gap of a spark plug is outside the specified range, replace the spark plug.
In addition, replace spark plugs that shows excessive dirt deposit or broken insulators.

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Engine Management – V6 – Service Operations Page 6C1-3–49

1 Replace any plug that has cracked and / or broken insulation or loose electrodes.
2 Inspect the spark plugs for defects. Refer to Analysis of Spark Plug Condition in this Section for identification of the condition of spark plugs.
3 Ensure the threads are clean and in good order.
4 Use a round wire feeler gauge to check the spark plug gap. If the gap is not within specifications, replace the
spark plug.
Spark plug gap ........................................... 1.1 – 1.2 mm
Figure 6C1-3 – 68
Spark Plug Inspection
Poor Spark Plug Performance
A spark plug can perform poorly due to wear, dirt, carbon fouling, excessive electrode wear, a broken insulator or
excessive gap.
Worn or Dirty Plugs
W orn or dirty plugs can give satisfactory operation while the vehicle is idling, but break down under load.
This can cause:
• poor fuel economy,
• power loss,
• acceleration loss,
• difficult starting, or
• poor engine performance.
Carbon Fouling
Carbon fouling is indicated by black carbon deposits. The black deposits are usually the result of slow-speed driving and
short runs. In these circumstances, the optimum engine operating temperature is seldom reached.
Fouling can also be caused by:
• worn piston rings,
• faulty ignition,
• rich fuel mixture, or
• spark plugs that are rated too cold.
Excessive Electrode Wear
This often indicates:
• the engine is operating at high speeds,
• the engine is operating at levels that are consistently greater than normal,
• a plug that is rated too hot,
• excessively lean fuel mixture, or

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Engine Management – V6 – Service Operations Page 6C1-3–50

• plug/s overheating due to insufficient tightening (caused by combustion gases leaking past the threads).
Broken Insulator
Broken insulators are usually the result of improper installation or carelessness.
Breaks in the upper insulator can result from a poor fitting spark plug socket or impact. The cracked insulator may not
show up until oil or moisture penetrates the crack. The crack is often just below the crimped part of the shell and may not
be visible.
Breaks in the lower insulator often result from careless re-gapping and are usually visible.
This can also result from the plug operating too hot. For example, in periods of high speed operation or under heavy
loads.

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Engine Management – V6 – Service Operations Page 6C1-3–51

Analysis of Spark Plug Condition

Figure 6C1-3 – 69
Legend
1 Normal
2 Carbon Fouled
3 Oil Fouled
4 Deposit Fouling A 5 Deposit Fouling B
6 Deposit Fouling C
7 Detonation
8 Pre-ignition 9 Heat Shock Failure
10 Insufficient Installation Torque

Normal Operation (1)
Brown or greyish-tan deposits and slight electrode wear indicate correct spark plug heat range and mixed periods of high
and low speed driving.
Carbon Fouled (2)
Dry, fluffy black carbon deposits possibly due to poor ignition output, a weak coil, excessive idling or slow speeds under
light load. If spark plug temperatures remain too low for normal combustion, the deposits are not burned off.

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Engine Management – V6 – Service Operations Page 6C1-3–52

Oil Fouled (3)
W et, oily deposits with minor electrode wear possibly due to oil leaking past worn piston rings.
Breaking in a new or recently overhauled engine before the rings are fully seated may also result in this condition.
Deposit Fouling A (4)
Red brown, yellow and white coloured coatings on the insulator tip which are by-products of combustion. They come
from fuel and lubricating oil which generally contain additives. Most powdery deposits have no adverse effect on spark
plug operation, however, they may cause intermittent missing under severe operating conditions.
Deposit Fouling B (5)
Deposits similar to those identified in deposit fouling A (4). These are also by-products of combustion from fuel and
lubricating oil. Excessive valve stem clearances and / or defective intake valve seals allow too much oil to enter the
combustion chamber. The deposits will accumulate on the portion of the spark plug that projects into the chamber and
will be heaviest on the side facing the intake valve. If this condition is only detected in one or two cylinders, check the
valve stem seals.
Deposit Fouling C (6)
Most powdery deposits identified in deposit fouling A (4) have no adverse effect on the operation of the spark plug as
long as they remain powdery.
Under certain conditions of operation however, these deposits melt and form a shiny glaze coating on the insulator.
W hen hot, this acts as a good electrical conductor allowing the current to flow along the deposit instead of sparking
across the gap.
Detonation (7)
Commonly referred to as engine knock or pinging, detonation causes severe shocks inside the combustion chamber
causing damage to parts.
Pre-ignition (8)
Burnt or blistered insulator tip and badly eroded electrodes probably due to the excessive heat.
This is often caused by a cooling system blockage, sticking valves, improperly installed spark plugs or plugs that are the
wrong heat rating (too hot).
Sustained high speed with a heavy load can produce temperatures high enough to cause pre-ignition.
Heat Shock Failure (9)
A rapid increase in spark plug tip temperature under severe operating conditions can cause heat shock and result in
fractured insulators. This is a common cause of broken and cracked insulator tips.
Insufficient Installation Torque (10)
Poor contact between the spark plug and the cylinder head seat.
The lack of proper heat transfer that results from poor seat contact causes overheating of the spark plug. In many cases,
severe damage occurs. Dirty threads in the cylinder head can cause the plug to seize before it is seated.
Ensure the cylinder head and spark plug threads are free of deposits, burrs and scale before installation.

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Engine Management – V6 – Service Operations Page 6C1-3–53

Reinstall
Reinstallation of the spark plug is the reverse of the removal procedure, noting the following:

• Discard the spark plug if it has been
dropped.
• Do not use anti-seize compound or similar
lubricant on the spark plug threads.
1 Using a suitably sized rubber tube attached to the spark plug terminal post, hand start each spark plug into the cylinder head thread.

Failure to tighten a spark plug to the correct
torque specification may result in premature
spark plug failure, and / or engine damage.
2 Tighten the spark plug/s to the correct torque specification. Spark plug torque specification ...............16.0 – 20.0 Nm
3 Road test the vehicle and check for correct operation.
2.23 Throttle Body Assembly
Handling Precautions

Under no circumstances should the clip (1),
six places, retaining the cover plate (2) to the
throttle body be removed. If the cover is
removed, the vacuum seal between the cover
plate and the throttle body will be broken.
This will allow the ingress of foreign particles
and / or moisture and render the throttle body
unserviceable
The throttle body must not be subjected to
any form of shock such as dropping it. If the
throttle body is subjected to shock, damage
may result to the fragile motor magnets
within the throttle body.
Figure 6C1-3 – 70
Remove
1 Turn the ignition switch off.

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Engine Management – V6 – Service Operations Page 6C1-3–54

2 Loosen the air intake duct to throttle body assembly
retaining clamp (1).
3 Pull the air intake duct (2) away from the throttle body assembly.
NOTE
If difficulty is experienced in removing the air
intake duct from the throttle body, completely
remove the air intake duct assembly, refer to
2.16 Intake Air Duct Assembly.
Figure 6C1-3 – 71
4 Unclip the wiring harness from the retaining clip (1).

Do not use any mechanical device such as a
screwdriver to disengage the harness
connector (2) from the throttle body.
5 Disconnect the wiring harness connector by: NOTE
When sliding the connector lock, take care not to
disengage it from the connector.
• Sliding the connector lock (3) in the direction of
the arrow, then
• press the connector latch in the direction of the
arrow (4), and remove the connector from the
throttle body.
Figure 6C1-3 – 72
6 Remove the four bolts (1), attaching the throttle body (2) to the upper intake manifold (3).
7 Remove the throttle body and gasket (4).
Figure 6C1-3 – 73

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Engine Management – V6 – Service Operations Page 6C1-3–55

Inspect
The following throttle body inspection procedure may be carried out with the throttle body installed on the vehicle. Prior to
performing a throttle body on-vehicle inspection:
• Turn the ignition switch off.
• Disconnect the throttle body wiring harness connector. Refer to Remove in this Section.
• Remove the air intake duct, refer to 2.16 Intake Air Duct Assembly.

To avoid serious personal injury, never
attempt to rotate the throttle plate manually
whilst the throttle body harness connector is
connected to the throttle body.
1 Fully open the throttle plate by hand and inspect the throttle body bore and throttle plate for any deposits.

When cleaning / inspecting the throttle body:
• Do not subject the throttle body assembly
to an immersion cleaner or a strong
solvent. Damage to the throttle position
sensor and / or sealed throttle shaft
bearings will result.
• Never use a wire brush or scraper to clean
the throttle body. A wire brush or sharp
tool may damage the throttle body
components.
2 Use a clean shop towel and a spray type hydro-carbon cleaner to clean the throttle body bore and throttle plate. If necessary, use a parts cleaning brush to remove heavy deposits.
3 Inspect the throttle body for a binding throttle plate by fully opening and closing the throttle plate by hand. It should open and close smoothly.
4 Inspect the throttle body for a bent or damaged throttle plate, cracks, corrosion, or distortion in the throttle body housing.
NOTE
The throttle body contains no serviceable parts
and should not be disassembled. If the throttle
body is damaged it must be replaced as an
assembly.
5 If the throttle body is affected by any of the above conditions, it must be replaced.
6 If an on-vehicle throttle body inspection was performed, perform the following:
• Reinstall the air intake duct, refer to 2.16 Intake Air Duct Assembly.
• Reconnect the throttle body wiring harness connector, refer to Reinstall in this Section.
• Road test the vehicle and check for correct operation, taking particular note that no air leaks are evident.
Reinstall
Reinstallation of the throttle body assembly is the reverse of the removal procedure, noting the following:
1 Ensure the throttle body and upper intake manifold mating surfaces are clean and free of foreign material.
2 Install a new throttle body to upper intake manifold gasket.

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