What Causes Low Idle Speed in Cars?

[AlexandraLynn]

Common causes of low idle speed in cars are as follows: 1. Oil accumulation and carbon deposits in the throttle body, or dirty intake passages: As the car is used over time, the intake passages can become clogged, and carbon deposits or oil may accumulate in the throttle body, leading to unstable idle speed or even low idle speed. Carbon deposits in the throttle body can affect the air intake volume, and the car may also exhibit low idle speed when starting cold. 2. Weak spark due to faulty spark plugs: Over time, spark plugs can also develop carbon deposits. When the carbon buildup is severe, the spark from some spark plugs may weaken, affecting the car's performance and causing low idle speed. It is recommended to clean or replace the spark plugs promptly. 3. Faulty idle control valve: When the car's related sensors malfunction, the car may not achieve the correct air-fuel ratio. Common sensor failures include the coolant temperature sensor, oxygen sensor, and throttle position sensor, leading to high fuel consumption and low idle speed.