Reasons for Engine Stalling After Cold Start Shaking

[Andrew]

Engine stalling after cold start shaking is caused by carbon buildup. Below is a detailed explanation of this issue: 1. The primary cause of engine stalling after cold start shaking is carbon deposits. Carbon buildup typically occurs in several areas: the inner walls of the throttle body, the intake valve heads, the inner walls of the intake manifold, the piston tops, and the inner walls of the combustion chamber. Excessive carbon deposits on the throttle body walls can restrict airflow, making starting difficult or causing the engine to stall easily at idle. 2. After the coolant reaches normal operating temperature, if the throttle opening exceeds normal idle values, the ECU will repeatedly adjust the throttle plate position, resulting in unstable idle speed fluctuations. The most prone area for carbon buildup isn't just the throttle body, but particularly the intake valve heads (at the end of the intake ports). 3. More seriously, if excessive carbon accumulates on intake valve heads, it can prevent proper valve sealing, making cold starts even more difficult. Even if the engine manages to start, it may stall quickly. Additionally, as engine temperature rises, the fuel absorbed in these carbon deposits evaporates and gets drawn into the cylinders for combustion. This uncontrolled fuel supply leads to an overly rich air-fuel mixture, further causing poor engine performance.