What Causes Severe Idle Vibration in Subaru Legacy?

[VonValentina]

Severe idle vibration in a Subaru Legacy may be caused by engine intake pipe leaks, fuel system blockages or malfunctions, or idle control valve failure. Engine intake pipe leak: The intake system contains numerous intake pipes and valves. If a leak occurs, it can lead to excessively high or low concentrations of the air-fuel mixture in the intake manifold, resulting in intermittent engine vibration or weak idle performance. Fuel system blockage or malfunction: Blockages in areas such as the fuel tank vent or fuel lines can prevent the engine from receiving the appropriate amount of fuel during idle. This causes the air-fuel mixture to become lean, weakening engine power output and leading to idle vibration. Idle control valve failure: In fuel-injected engines, idle operation is primarily controlled by the idle control valve. The ECU regulates the opening of the idle control valve based on signals such as engine speed, temperature, and throttle position to maintain stable engine idle. If the valve fails, it can cause uneven air distribution, resulting in fluctuating idle power and vehicle vibration.