Unstable Idle Speed of China IV EFI Motorcycle
1 Answers
The reasons for unstable idle speed in China IV EFI motorcycles are as follows: 1. Throttle body carbon deposits: Carbon buildup on the throttle body affects its opening degree and air intake volume, causing the engine speed to fluctuate between high and low after cold starts, resulting in extreme instability accompanied by vibrations. 2. Low fuel pressure or intake manifold leakage: Issues such as clogged fuel injectors, blocked fuel lines, insufficient fuel pump pressure, or faulty fuel pressure regulators can lead to poor atomization, abnormal air-fuel mixture ratios, and incomplete combustion, resulting in unstable idle speed. Intake manifold leaks can distort the feedback data from the intake pressure sensor, causing the ECU to inaccurately control the air intake and leading to abnormal air-fuel mixtures, which further destabilizes the engine idle. Additionally, a malfunctioning or stuck stepper motor can also cause idle instability. 3. Sensor failures: Faulty sensors can prevent precise control of the air-fuel ratio, such as issues with the intake air temperature sensor, oxygen sensor, throttle position sensor, or intake pressure sensor. For example, if the actual intake air temperature is 5°C but the sensor erroneously reports 30°C to the ECU, the ECU will command the fuel injectors to reduce fuel supply, causing excessively low idle speed or even no idle at all.
