Reasons for High Idle Speed in Alto
2 Answers
Alto's high idle speed during cold starts is a normal phenomenon. More details about high idle speed during cold starts are as follows: 1. The purpose of high idle speed during cold starts is to allow the car to reach normal operating temperature as quickly as possible. After warming up, the idle speed will return to normal values. 2. Engine wear at low temperatures is more severe than at normal temperatures, and gasoline atomization is less complete at low temperatures, resulting in slightly poorer combustion conditions in the cylinders. 3. Generally, the lower the ambient temperature, the longer the high idle speed will persist. The normal idle speed after the engine warms up is usually around 800~900 rpm.
That time when I was driving my Alto and encountered the idle speed suddenly surging to 2000 RPM, I went straight to my trusted repair shop to check three key areas. The throttle body on older cars is most prone to carbon buildup—after taking it apart myself, sure enough, it was covered in black grime. Cleaning it immediately brought the RPM down. The mechanic even showed me how to feel the hose behind the throttle body, explaining that air leaks could also cause high idle speeds, and we discovered a small crack hissing with escaping air. Finally, we tested the coolant temperature sensor data—if this fails, the engine misjudges the temperature and keeps revving unnecessarily. His advice: start by cleaning the throttle body, then check for air leaks. At a small shop, the whole job, including labor and parts, only cost around 200–300 RMB. But don’t delay—otherwise, the fuel consumption will shock you.
