Car Stalling at Traffic Lights?
Find Out What’s Wrong

The most common cause of stalling at idle on modern petrol engines. Carbon deposits build up on the throttle plate and bore — reducing airflow to the point where the engine cannot sustain idle. The throttle body sensor also reads incorrectly when dirty. Professional cleaning with throttle body cleaner resolves the issue in most cases without needing replacement.

The idle air control valve regulates air supply to the engine at idle to maintain a stable idle speed. A sticking or failed IAC valve causes the idle to drop too low — stalling the engine when decelerating to a stop. Cleaning or replacement of the valve resolves the issue.

A weak fuel pump or blocked fuel filter can cause stalling under light load conditions — such as idling at traffic lights when fuel demand is low but consistent. Fuel pressure testing confirms whether delivery is adequate.

An incorrect reading from the mass airflow sensor causes the ECU to miscalculate fuelling at idle — resulting in a lean mixture that cannot sustain combustion at low revs. The engine stalls. Cleaning the MAF sensor often resolves the issue.

Unmetered air entering the intake through a split hose or loose connection leans out the mixture at idle — causing rough idle and stalling. Vacuum leaks are often accompanied by a hissing sound from the engine bay and a high or hunting idle.