What Causes Engine Idle Stalling?

[DeMaverick]

Here are the reasons for engine idle stalling: 1. Ignition system failure: Issues with components such as the ignition coil, ignition module, ignition ECU, distributor, ignition signal generator, sensors affecting ignition timing, or high-voltage wires can lead to misfires, weak sparks, or incorrect ignition timing, resulting in poor idle performance. 2. Neutral start switch circuit: In vehicles equipped with automatic transmissions, the ECU adjusts the idle speed based on signals from the neutral start switch. When the gear selector is in reverse or drive, the idle speed is automatically increased; otherwise, it is decreased. A faulty neutral start switch circuit can cause the ECU to receive incorrect signals, leading to excessively high or low idle speeds. 3. Fuel pump and fuel system: The fuel pump and fuel system affect fuel pressure. If the pressure is too low, the actual fuel injection volume decreases under the same energizing time of the injector coil, resulting in poorer spray quality and a lean idle mixture. Conversely, if the pressure is too high, excessive fuel injection occurs, leading to a rich mixture. Fuel system pressure is related to the technical condition of the fuel pressure regulator, fuel pump, fuel pressure solenoid valve, and their circuit operation.

[Kenneth]

There are quite a few reasons for engine stalling at idle. After years of driving, I've summarized several key points: First is fuel system issues – if the fuel pump is aging or the fuel injectors are clogged, insufficient fuel supply can cause stalling at idle. Second is intake system problems, such as a dirty air filter or air leaks in the piping, which can lead to insufficient oxygen intake. Third is electrical faults – worn spark plugs or faulty ignition coils can prevent proper ignition. Fourth is sensor malfunctions – if components like the idle air control valve fail to operate or the throttle position sensor has issues, idle speed becomes unstable. Another common cause is vacuum leaks in the hoses, which directly affect idle RPM. Such situations require immediate attention, as sudden stalling at traffic lights could potentially cause rear-end collisions. I recommend first checking simple components like the air filter, then having a professional mechanic test the electrical circuits.