What Causes Unstable Idle Speed When the Engine is Cold?
1 Answers
Car unstable idle speed during cold start may be caused by air intake system leaks, low fuel pressure, clogged air filter, injector atomization leakage, improper idle adjustment, faulty spark plugs, air flow meter malfunction, etc. Here is a detailed explanation: 1. In cold conditions, the car needs to bring the engine into normal operating conditions as quickly as possible after starting. Therefore, during cold starts, the engine control unit automatically injects more fuel to rapidly increase the engine's water temperature by burning more fuel than normal idle speed, allowing the engine to quickly reach the appropriate temperature. 2. The main manifestation is that the engine idle speed will be relatively high when cold, generally between 950-1300 RPM. When the engine temperature rises to a certain value, the idle speed will decrease to the normal level. 3. Under normal circumstances, the engine's air intake must be strictly limited. If there are abnormalities or leaks in the intake system, throttle valve, air flow meter, or idle control valve, it may cause unstable engine idle speed. 4. The same applies to the fuel injection system. If the electronic control unit receives incorrect signals and misjudges the car's operating conditions, it may lead to abnormal fuel injection. 5. Additionally, clogged fuel injectors can also cause a decrease in engine power and unstable idle speed.
