What are the reasons for high idle speed in small cars?
2 Answers
Small cars have high idle speed for the following reasons: 1. High idle speed causes: When the engine water temperature is low, the air conditioning is on, or the engine voltage is low, the ECU program is designed to appropriately increase the idle speed, which is normal. If the engine water temperature is normal, the air conditioning is off, and the idle speed is still high, it indicates a system malfunction, which could be either in the electronic control system or the mechanical system. 2. Mechanical faults: For mechanical faults causing high idle speed, it is essential to check for air leaks in the intake pipe, detached or damaged vacuum tubes, or damaged intake pipes. The intake manifolds of Volkswagen engines are mostly rubber pipes. During idle, the engine intake air volume is minimal, and any air leaks can result in high idle speed.
The other day my car's idle speed suddenly increased, with the tachometer jumping to nearly 1000 RPM, making the ride extremely uncomfortable. Common causes of high idle speed include a dirty or stuck throttle body—dust buildup over mileage can affect air intake. A faulty mass airflow sensor can also cause this; it normally controls the air intake volume, and if broken, the engine may draw more fuel to maintain operation. Air leaks in the intake system, like cracked or aged hoses, or a malfunctioning idle control valve, are other culprits. Don't ignore this issue—high idle not only wastes fuel and increases costs but may also accelerate engine wear. When checking, I first inspect the throttle body for carbon buildup; sometimes manual cleaning suffices. If that doesn't work, it's best to visit a professional shop for an ECU scan—it could be a software bug or other faults. In short, high idle is a warning sign; timely detection and action can prevent costly major repairs.
