What are the causes of low vehicle idle speed?

[Natasha]

Reasons for low vehicle idle speed: 1. Oil accumulation and carbon deposits in the throttle body, dirty intake tract: As the vehicle usage time extends, the intake tract may become clogged, with carbon deposits or oil present in the throttle body, leading to unstable idle speed or even low idle speed. Carbon deposits in the throttle body affect the air intake volume, causing low idle speed during cold starts. It is recommended to clean the throttle body and intake tract to prevent abnormal idle conditions. 2. Weak spark due to faulty spark plugs: Over time, spark plugs can also accumulate carbon deposits. When severely carbon-fouled, weak sparks from individual cylinder spark plugs can affect vehicle performance, resulting in low idle speed. Timely cleaning or replacement of spark plugs is advised. 3. Fuel system blockage represented by clogged fuel injectors, or intake manifold malfunction: When fuel injectors are clogged, the vehicle may experience fuel supply pressure issues and poor fuel atomization, leading to unstable or low idle speed. If the intake manifold malfunctions, the air-fuel mixture ratio becomes imbalanced, potentially causing excessive emissions and failure in annual vehicle inspections. 4. Malfunction of related sensors: When vehicle sensors fail, the correct air-fuel ratio cannot be maintained. Common issues include faulty coolant temperature sensors, oxygen sensors, throttle position sensors, etc., resulting in high fuel consumption and low idle speed.