What is the reason for the low idle speed at the start of cold car?

The reasons of low idle speed in cold start are: carbon deposition in throttle, unclean air intake and weak spark caused by individual spark plug failure. Spark plugs should be cleaned or replaced in time. The following reasons are relevant: 1. When the car is used for a long time, the air inlet will be blocked, and the throttle will have carbon or engine oil, which will cause the phenomenon of unstable idle speed or even low idle speed. The throttle will affect the air intake due to carbon deposition, and the car will also have a low idle speed when starting. It is suggested that the owner clean the throttle and air intake of the car to avoid abnormal idling of the car. 2. With the extension of service time, there will be carbon deposition in automobile spark plugs. When the carbon deposition is serious, the spark plug on individual cylinders will be weak, which will affect the performance of the vehicle and lead to the phenomenon of low idle speed of the vehicle. It is recommended to clean or replace the spark plug in time. 3. When the fuel nozzle of the automobile is blocked, there will be poor fuel supply pressure and fuel atomization in the automobile, which will lead to unstable or low idle speed of the automobile. When the intake pipe of a car fails, the proportion of mixed gas is unbalanced, which may lead to excessive emissions and unqualified annual inspection of the car.