What are the symptoms of unstable engine idle speed?
1 Answers
Unstable idle speed of a car engine mainly manifests in the following aspects: 1. The tachometer needle fluctuates up and down during idle, showing instability. 2. Vibration occurs during idle. The following are the reasons for unstable idle speed: 1. Clogged fuel injector: Leads to insufficient fuel supply pressure. Clogging of fuel injectors is usually caused by gum and carbon deposits in gasoline. 2. Faulty water temperature sensor: The car's water temperature sensor is generally installed on the engine block (or possibly on the water jacket of the cylinder head) and directly contacts the coolant (antifreeze) to measure the temperature of the engine coolant. Once the water temperature sensor fails, the car may experience unstable idle speed, difficulty starting when cold, inability to increase speed, and significantly increased fuel consumption. 3. Faulty throttle position sensor: The throttle position sensor detects whether the engine is in idle condition or under load operation, and whether the car is accelerating or decelerating. Damage to the throttle position sensor can cause engine vibration and unstable idle speed. 4. Air intake system leakage: The ECU controls the mixture concentration primarily based on intake air information such as water temperature, throttle opening, and engine speed provided by the air flow meter. Leakage in the intake air system can cause the ECU to inaccurately control the intake air volume, leading to unstable engine idle speed. 5. Exhaust system blockage: Causes poor exhaust, resulting in symptoms such as weak acceleration, reduced power, and unstable idle speed. 6. Weak spark from individual spark plugs: Leads to cylinder misfire, causing unstable engine idle speed, and may also result in black smoke from the exhaust pipe, reduced power, and backfiring.
