Why Does the Idle Ignition Angle Keep Fluctuating?
2 Answers
The reasons for the continuous fluctuation of the idle ignition angle include severe engine carbon deposits, ignition system issues, and unstable oil pressure. Severe Engine Carbon Deposits: When there is excessive carbon buildup inside the engine, the gasoline sprayed by the cold-start fuel injector can be largely absorbed by the carbon deposits. This results in an overly lean air-fuel mixture during cold starts, making it difficult to start the engine. Under such conditions, the engine will only start easily once the carbon deposits have absorbed enough gasoline to reach saturation. After starting, the gasoline adsorbed on the carbon deposits is then drawn into the combustion chamber by the engine's vacuum, causing the air-fuel mixture to become overly rich. This alternation between lean and rich mixtures leads to fluctuations in the idle ignition angle after a cold start. The lower the temperature, the more fuel is required for a cold start, and the presence of carbon deposits significantly impacts the success of the cold start. Ignition System Issues: Inspect the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or inadequate spark plug firing can also cause such symptoms. Unstable Oil Pressure: If the idle ignition angle continues to fluctuate even after cleaning the engine carbon deposits, washing the throttle body, replacing the oil gasket and spark plugs, etc., it is recommended to visit a 4S shop to check the fuel supply pressure and the intake pressure sensor for any abnormalities.
The continuous fluctuation of ignition timing at idle is usually related to the engine control unit constantly making adjustments. When the engine is idling, the ECU monitors various parameters to optimize performance. If signals from sensors like the crankshaft position sensor are unstable, it may misjudge RPM changes and continuously correct the ignition timing. Alternatively, if the mass airflow sensor is clogged with dirt and affects the calculation of air intake, the ECU will keep fine-tuning. Fuel system issues, such as dirty fuel injectors, can also trigger repeated compensation. Rapid temperature changes or unstable battery voltage can amplify this phenomenon, causing the engine to sound rough. It is recommended to use a diagnostic tool to read fault codes as soon as possible to check if key sensors are drifting, and to clean carbon deposits to maintain circuit cleanliness and avoid more severe power issues.
