What Causes High Idle Speed in Cold Weather?
2 Answers
When starting a car in cold weather, the reasons for high idle speed are as follows: 1. High idle speed during startup is a normal phenomenon: a. The car requires higher RPM to allow the engine to reach normal operating conditions quickly. This necessitates a richer air-fuel mixture, leading to increased air intake and fuel injection, which results in higher RPM. b. Increased oil viscosity during cold starts: During a cold start, the idle stepper motor automatically adjusts to increase air intake, allowing more air to enter the cylinders. High idle speed is normal in this situation. 2. Excessive carbon buildup: Timely cleaning of the throttle body and idle speed control valve can generally resolve this issue.
Actually, high idle speed in cold weather is quite common, mainly because the engine wants to warm up quickly to protect its components. The ECU detects the cold coolant through the temperature sensor and automatically increases the idle speed to 1500 RPM or higher, allowing the oil to circulate and lubricate faster, avoiding cold start wear or stalling risks. Once the temperature rises to the operating point, the speed gradually drops back to normal, such as around 800 RPM. If the idle speed remains high and doesn't come down, it might be due to a faulty sensor or carbon buildup in the throttle body, which needs to be checked and repaired. A temporarily high idle speed consumes a bit more fuel, but it's a normal phenomenon—no need to panic, just wait a few more minutes and it'll be fine.