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.

[ONevaeh]

I've experienced engine stalling at idle several times. That time when I was waiting at a red light, the engine suddenly died - really scary. Later during repairs, we found the idle control valve was severely carbon-fouled, causing it to jam and become unresponsive. Some older cars with worn-out spark plugs are also prone to this - unstable ignition leads to stalling. Other causes include fuel delivery issues; a clogged fuel filter can't supply enough fuel, especially noticeable at idle. If sensors like the crankshaft position sensor fail, causing unstable ECU control, stalling can occur. A dirty mass airflow sensor can also cause problems. My advice: don't force a restart, first check the fuses, then try replacing the faulty component. Always pay attention to unusual engine noises - any abnormal sounds should prompt immediate inspection to prevent more serious damage.

[MacCharles]

Here are several common causes of engine stalling at idle: insufficient fuel supply possibly due to a faulty fuel pump; ignition system issues such as bad spark plugs or leaking high-voltage wires; air system malfunctions like clogged air filters or air leaks in the pipes; sensor problems including a damaged idle control valve or incorrect throttle position; and engine vacuum leaks. If you encounter this issue, first perform a simple test to see if the RPM fluctuates significantly at idle, then check if the lights or fuses are functioning properly. It's recommended to take the car to a shop for an OBD scan to identify the specific cause—avoid disassembling parts yourself as it may cause further damage. Regular cleaning of fuel injectors and throttle bodies can help prevent this issue. Safety first!