Isuzu N 2008 Series Workshop Manual page 332

Checks
Air Intake System Checks
Exhaust System Checks
Engine Mechanical Checks
Additional Checks
Inspect the air intake system for the following conditions.
• Air cleaner, air intake ducts and charge air cooler for a restriction, holes, or leaks.
• A restriction in the turbocharger inlet duct.
• Intake throttle valve for a stuck condition.
• A restriction or leak in the intake manifold.
Inspect the exhaust system for a possible restriction. Refer to Exhaust System in
Section 1G Engine Exhaust.
Inspect the engine mechanical for the following conditions. Refer to Section 1B Engine
Mechanical.
• Poor cylinder compression.
• Improper mechanical timing (timing gear and timing chain).
• Improper valve gap.
• Broken or weak valve springs.
• Worn camshaft lobes.
• Incorrect basic engine parts such as camshaft, cylinder head, pistons, etc.
• Electromagnetic interference (EMI) on the reference circuit can cause an engine
miss condition. The scan tool can usually detect EMI by monitoring the engine
speed. A sudden increase in speed with little change in actual engine speed change
indicates that EMI is present. If a problem exists, check routing of high voltage
components, such as fuel injector solenoid valve wiring, near the sensor circuits.
• Faulty engine mounts.
• Faulty crank pulley.
• Faulty generator & A/C compressor.
• Generator output voltage.
• EGR system operating correctly. Refer to EGR Control System Check in this
section.
• A/C operation.
Engine Control System (4JJ1)
Action
1A-329