What Causes a Car to Start Immediately When Cold but Not When Hot?
1 Answers
The reasons why a car starts immediately when cold but not when hot are: 1. Carbon deposits: At high temperatures, carbon deposits have a strong adsorption effect on gasoline. If there are excessive carbon deposits on the intake valve, throttle valve, or piston, they can adsorb some fuel, leading to an overly lean air-fuel mixture and affecting startup. 2. Coolant temperature sensor: The coolant temperature sensor adjusts the fuel injection pulse width. If it malfunctions and fails to provide the correct temperature signal, it will affect the engine's fuel injection, causing an abnormal air-fuel ratio and making startup difficult. 3. Intake air temperature sensor: Similar to the coolant temperature sensor, the intake air temperature sensor also adjusts the fuel injection quantity. A higher intake air temperature sensor reading results in a richer mixture, while an open circuit or poor grounding can cause an overly lean mixture. Both overly rich and lean mixtures can make starting difficult. 4. Fuel quality issues: After a hot engine shutdown, the engine compartment remains at a high temperature. If the fuel is prone to evaporation, it can form high vapor pressure in the fuel rail. When this pressure exceeds the fuel system's pressure, it creates vapor lock, causing the fuel injector to spray overly lean fuel vapor, making starting difficult. 5. Fuel injector leakage: Due to the high temperature immediately after engine shutdown, leaking fuel can turn into vapor and enter the intake manifold. A hot start under these conditions can result in an overly rich mixture, making starting difficult.
