Why does the idle speed become higher after starting the car in hot summer?
2 Answers
Here are the reasons why the idle speed becomes higher after starting the car in hot summer: 1. The greater the temperature difference, the higher the speed: Higher idle speed at startup is a normal phenomenon. The car needs a higher speed to allow the engine to reach normal operating conditions as soon as possible, requiring a richer air-fuel mixture, so both the intake air volume and fuel injection volume will increase, leading to a higher speed. To save fuel and reduce wear during startup, there is generally a cold fast idle or water temperature sensor. The colder the weather and the lower the water temperature (compared to the normal operating temperature of the engine, generally around 85-110 degrees), the greater the temperature difference from the normal engine operating temperature, and the computer will control the cold fast idle to be higher, meaning the engine speed will be higher at startup. 2. Excessive carbon deposits: High speed is generally caused by excessive carbon deposits. Timely cleaning of the throttle and idle speed motor can generally solve the problem.
When I worked at the repair shop, I often encountered car owners reporting this issue. After the car is exposed to the sun in summer, the idle speed becomes higher, mainly because the engine compartment temperature is too high. The ECU protects the engine by automatically injecting more fuel to increase the RPM, which helps drive the water pump and fan to dissipate heat faster. Additionally, the activation of the air conditioning compressor also increases the engine load, forcing the ECU to raise the RPM to compensate. Moreover, gasoline tends to vaporize in high temperatures, forming vapor lock, which can disrupt fuel supply in the fuel lines. The ECU then adjusts the idle speed to maintain balance. These are all normal, and the idle speed will stabilize after a few minutes of driving as the coolant temperature drops. However, if the idle speed remains consistently high or the car shakes, it might be necessary to check the coolant temperature sensor or the fuel lines.
