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