Why is the idle speed high during cold start?
2 Answers
Cars have high idle speed during cold start for the following reasons: 1. High idle speed during startup is normal: (1) The car needs high speed to make the engine reach normal working conditions as soon as possible, requiring a richer mixture, so the intake air volume and fuel injection volume will increase, resulting in higher speed. (2) Increased oil viscosity during cold start: During cold start, the idle stepper motor automatically adjusts to increase the intake air volume, allowing more air to enter the cylinder, so high idle speed is normal. 2. Excessive carbon deposits: Timely cleaning of the throttle and idle motor can generally solve this problem.
I've been driving for over a decade, and high idle speed during cold starts is very common. When the engine is cold, it needs to increase RPM to warm up quickly so the catalytic converter can work effectively. The idle speed usually drops after a few minutes. However, if the idle speed remains above 2000 RPM for an extended period or is accompanied by shaking, it could indicate a faulty coolant temperature sensor, a vacuum leak, or a dirty throttle body. I've seen many car owners ignore such minor issues, only to face skyrocketing fuel consumption or even engine stalling later. That's why I recommend having a technician scan for trouble codes during every maintenance check to address problems early. While it's normal and nothing to worry about, persistent abnormalities should be taken seriously to avoid breakdowns on the road.
