Kawasaki Vulcan idling low and high.

1. When the engine water temperature is low, the air conditioner is turned on, and the engine voltage is low, ECU programming should appropriately increase the idle speed. Under this normal condition, if the engine water temperature is normal, the air conditioner is not turned on, and the idle speed is high, it means that the system is faulty, which may be an electronic control system or a mechanical system.

2. If the idle speed is too high due to mechanical failure, be sure to check whether the intake pipe leaks, whether the vacuum pipe falls off and whether the intake pipe is damaged (the intake manifold of Volkswagen engine is mostly rubber pipe). Because the air intake of the engine is very small at idle speed, if there is air leakage, it will cause high idle speed.

3. Leakage of fuel injector may lead to excessive fuel supply, which may lead to higher idle speed than normal.

4. For EFI vehicles equipped with fuel vapor recovery system, fuel vapor should not enter the intake pipe at idle speed. If fuel vapor is sucked into the intake pipe at idle speed due to system failure, the idle speed is higher than normal.

5. After cleaning the throttle body and idle speed control valve, the engine may have a high idle speed after starting, which requires a learning process for the computer. Because the engine idle speed will decrease after the throttle body and idle speed control valve are dirty, in order to stabilize idle speed, ECU will control the opening of idle speed control valve or throttle valve to increase the intake air, thus stabilizing idle speed.