1. Faulty idle air control valve (IAC). The IAC valve controls the amount of air that bypasses the throttle plate when the engine is idling. If the IAC valve is faulty, it can cause the engine to stall when you stop at a red light or sign.
2. Vacuum leaks. A vacuum leak can cause the engine to run lean and stall when you come to a stop. Check all the vacuum hoses for cracks or disconnections.
3. Dirty throttle body. A dirty throttle body can also cause the engine to stall. Clean the throttle body with a throttle body cleaner.
4. Fuel injector problems. A faulty fuel injector can cause the engine to run rough and stall. Have the fuel injectors checked and cleaned if necessary.
5. Faulty fuel pump. A faulty fuel pump can also cause the engine to stall. Check the fuel pressure to see if it is within specifications.
6. Bad ignition wires or spark plugs: Worn-out spark plugs or faulty ignition wires can cause the engine to misfire and stall. Check the spark plugs and wires and replace them if necessary.
7. Clogged fuel filter. A clogged fuel filter can restrict the flow of fuel to the engine and cause it to stall. Replace the fuel filter if it is clogged.