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Holden Astra Misfire Faults

Tech Tip explaining some of the causes and fault finding procedures in diagnosing combustion misfires.

Causes:

Engine misfires and associated fault codes stored in the ECU memory can be a result of many electrical and or mechanical malfunctions.

For instance, a lean Air Fuel mixture due to excessive air leakage of a faulty EGR valve, incorrect output signal of a malfunctioning Air Mass Meter or insufficient or no spark output from the ignition coil pack are regularly experienced faults.

However, engine mechanical malfunctions resulting in engine misfires can also result in some of the above codes to be stored in the ECU memory.

Diagnosis:

Please ensure to complete all fundamental and preliminary checks. For instance, check for intake air leaks, manifold vacuum; engine compression (it is favourable to conduct a cylinder leakage test to confirm engine condition), ensure hydraulic cam followers are not malfunctioning i.e. holding intake or exhaust valves open.

We suggest that a fuel pressure and flow test be conducted and thoroughly check any other possible causes that can result in an engine misfire which isn’t directly related to the engine management system.

1. Mass Air Flow Sensor

2. Throttle Motor

3. EGR Motor

4. ECU/ECM

5. Engine Control/Fuel Pump Relay

6. Ignition Coil Assy

7. Camshaft Position Sensor

8. Crankshaft Position Sensor