What Causes Difficulty Starting a Cold Engine but Easy Starting When Warm?

[VonReed]

The reasons for difficulty starting a cold engine but easy starting when warm include: 1. Excessive carbon buildup in the idle motor, intake tract, intake valves, and combustion chamber. When the intake tract is heavily fouled with carbon deposits, the cross-sectional area of the air passage changes, leading to either overly rich or overly lean air-fuel mixtures; 2. Issues with the fuel injectors, such as leaks or excessive carbon buildup, resulting in a lean mixture during startup, causing abnormal combustion or engine shaking after startup, or even failure to start; 3. Malfunction of the carbon canister or carbon canister solenoid valve; 4. High viscosity of engine oil or poor gasoline atomization; 5. The cold start injector not injecting fuel.