Isuzu KB P190. Manual — part 894

Engine Management – V6 – Service Operations

Page 6C1-3–52

Oil Fouled (3)

Wet, 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.
When 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.

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.

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.

N O T E

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:

N O T E

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

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.

N O T E

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.