Isuzu KB P190. Manual — part 702

Engine Mechanical – V6

Page 6A1–31

Page 6A1–31

2.2 Symptoms

Strategy Based Diagnosis

1

Review the system operations to familiarise yourself with the system functions, refer to

1 General Information

and

6C1-1 Engine Management General Information.

2

Perform an engine management Diagnostic System Check, refer to

Section 6C1-2 Engine Management – V6 –

Diagnostics

.

All diagnosis on a vehicle should follow a logical process. Strategy based diagnosis is a uniform approach for repairing
all vehicle systems. The strategy based diagnostic flow chart may always be used to resolve a system problem. The
diagnostic flow chart is the place to start when repairs are required. For a detailed explanation of strategy based
diagnosis and the flow chart, refer to

Section 6C1-2 Engine Management – V6 – Diagnostics

.

Visual / Physical Inspection

1

Inspect the vehicle for aftermarket accessories which may adversely affect engine operation.

2

Inspect the easily accessible or visible system components for obvious signs of damage or conditions that may
cause the symptom.

3

Check the engine lubrication system for the following:
•

correct oil level,

•

correct lubricant viscosity,

•

correct oil filter application, and

•

contaminated or burnt oil.

4

Confirm the exact operating conditions under which the fault occurs. Note factors such as:
•

engine speed (r.p.m.),

•

ambient temperature,

•

engine temperature,

•

engine warm-up time, and

•

vehicle road speed.

5

Compare the engine sounds, if applicable, to a known good engine, and ensure you are not trying to diagnose a
normal operating condition.

Intermittent

For intermittent faults, test the vehicle under the same conditions the customer reported in order to confirm whether the
system is operating correctly.

Engine Mechanical – V6

Page 6A1–32

Page 6A1–32

2.3

Engine Misfire without Internal Engine
Noises

Cause Correction

Abnormalities, severe cracking, bumps or missing areas in
the accessory drive belt.

Abnormalities in the accessory drive system and/or
components may cause engine speed variations that result
in a misfire diagnostic trouble code (DTC). A misfire code
may be present without an actual misfire condition.

Replace the accessory drive belt, refer to 3.5 Accessory
Drive Belt.

Refer to 6C1-2 Engine Management – V6 – Diagnostics to
check for DTCs.

Worn, damaged or misaligned accessory drive components
and excessive pulley run-out may lead to a misfire DTC.

A misfire code may be present without an actual misfire
condition.

Inspect the components and repair or replace as required.

Refer to 6C1-2 Engine Management – V6 – Diagnostics to
check for DTCs.

Loose or incorrectly fitted flexplate or crankshaft balancer
assembly.

A misfire DTC may be present without an actual misfire
condition.

Repair or replace the flexplate or crankshaft balancer as
required, refer to 3.13 Crankshaft Balancer Assembly or
4.3 Flexplate Assembly.

Refer to 6C1-2 Engine Management – V6 – Diagnostics to
check for DTCs

Restricted exhaust system.

A severe restriction in the exhaust flow can cause
significant loss of engine performance and may set a DTC.
Possible causes of restrictions in the exhaust system
include collapsed/dented pipes and blocked mufflers and/or
catalytic converters.

Repair or replace exhaust system components as required,
refer to 8B Exhaust System.

Refer to 6C1-2 Engine Management – V6 – Diagnostics to
check for DTCs

Incorrectly installed or damaged vacuum hoses.

Repair or replace vacuum hoses as required.

Incorrect sealing between the intake manifold and cylinder
heads, upper intake manifold and lower intake manifold,
throttle body and intake manifold.

Repair or replace the intake manifold, throttle body gaskets,
cylinder heads, throttle body as required.

Incorrectly installed or damaged barometric
pressure(BARO) sensor and/or seal. The seal should not
be torn or damaged.

Repair or replace the BARO sensor and/or seal as
required, refer to 6C1-3 Engine Management – V6 –
Service Operations.

Incorrectly installed or damaged EVAP purge solenoid
and/or O-ring seal.

Repair or replace the EVAP purge solenoid and/or seal as
required, refer to 6C1-3 Engine Management – V6 –
Service Operations

Worn or loose stationary hydraulic lash adjusters (SHLA)
and/or rocker arms.

The SHLAs, rocker arms and roller bearings should be
intact and in the correct position.

Replace the SHLAs and/or rocker arms as required, refer to
3.21 Stationary Hydraulic Lash Adjuster or 3.20 Rocker
Arm.

Stuck valves.

Carbon build up on the valve stems can result in the valves
not closing correctly.

Repair or replace as required, refer to 3.22 Cylinder Head
Assembly.

Excessively worn or misaligned timing chain/s.

Replace the timing chain/s and components as required,
refer to 3.16 Timing Chains, Tensioners, Shoes and
Guides.

Worn camshaft lobes.

Replace the camshaft/s and SHLAs as required, refer to
3.19 Camshaft or 3.21 Stationary Hydraulic Lash Adjuster.

Excessive oil pressure.

A lubrication system with excessive oil pressure may lead
to excessive lash adjuster pump-up and loss of
compression.

1

Perform an oil pressure test, refer to 3.1 Engine Oil.

2

Repair or replace the engine oil pump as required,
refer to 3.17 Oil Pump Assembly.

Engine Mechanical – V6

Page 6A1–33

Page 6A1–33

Cause Correction

Faulty cylinder head gasket and/or cracking or other
damage to the cylinder head and cylinder block coolant
passages.

Coolant consumption may or may not cause the engine to
overheat.

1

Inspect the spark plugs for coolant saturation, refer to
6C1-3 Engine Management – V6 – Service
Operations.

2

Inspect the cylinder heads, cylinder block and/or head
gaskets, refer to 3.22 Cylinder Head Assembly
and/or 4.7 Cylinder Block.

3

Repair or replace components as required.

Worn piston rings.

Oil consumption may or may not cause the engine to
misfire.

1

Inspect the spark plugs for oil deposits, refer to 6C1-3
Engine Management – V6 – Service Operations.

2

Check the cylinders for a loss of compression, refer to
2.15 Engine Compression Test.

3

Perform compression testing to identify the cause of
low compression.

4

Repair or replace components as required.

A damaged crankshaft reluctor wheel.

A damaged crankshaft reluctor wheel can result in different
symptoms depending on the severity and location of the
damage.

Systems with severe reluctor ring damage may exhibit
periodic loss of crankshaft position, stop delivering a signal,
and then re-sync the crankshaft position.

Systems with slight reluctor ring damage may exhibit no
loss of crankshaft position and no misfire may occur,
however, a DTC may set.

Replace the crankshaft as required, refer to 4.6 Crankshaft
and Main Bearings.

Refer to 6C1-2 Engine Management – V6 – Diagnostics to
check for DTCs

Engine Mechanical – V6

Page 6A1–34

Page 6A1–34

2.4

Engine Misfire with Abnormal Internal
Lower Engine Noises

Cause Correction

Abnormalities, severe cracking, bumps or missing areas in
the accessory drive belt.

Abnormalities in the accessory drive system and/or
components may cause engine speed variations that result
in a misfire diagnostic trouble code (DTC). A misfire code
may be present without an actual misfire condition.

Replace the accessory drive belt, refer to 3.5 Accessory
Drive Belt.

Refer to 6C1-2 Engine Management – V6 – Diagnostics to
check for DTCs

Worn, damaged or misaligned accessory drive components
and excessive pulley run-out may lead to a misfire DTC.

A misfire code may be present without an actual misfire
condition.

Inspect the components and repair or replace as required.

Refer to 6C1-2 Engine Management – V6 – Diagnostics to
check for DTCs

Loose or Incorrectly fitted flexplate or crankshaft balancer
assembly.

A misfire code may be present without an actual misfire
condition.

Repair or replace the flexplate or crankshaft balancer as
required, refer to 3.13 Crankshaft Balancer Assembly or
4.3 Flexplate Assembly.

Worn or broken piston rings.

Oil consumption may or may not cause an actual misfire.

1

Inspect the spark plugs for oil deposits, refer to 6C1-3
Engine Management – V6 – Service Operations.

2

Check the cylinders for a loss of compression, refer to
2.15 Engine Compression Test.

3

Perform compression testing to identify the cause of
low compression.

4

Repair or replace components as required.

Worn crankshaft thrust bearing.

Severely worn thrust surfaces on the crankshaft and/or
thrust bearing may permit fore and aft movement of the
crankshaft and create a DTC without an actual misfire
condition being present.

Replace the crankshaft and/or bearings as required, refer to
4.6 Crankshaft and Main Bearings.

Refer to 6C1-2 Engine Management – V6 – Diagnostics to
check for DTCs