Vacuum leaks: A vacuum leak can cause the engine to run lean and stall when you come to a stop. Check for any loose or cracked hoses or vacuum lines, particularly around the intake manifold and brake booster.
Idle Air Control (IAC) valve: The IAC valve regulates the amount of air that bypasses the throttle body to maintain a steady idle. A faulty IAC valve can cause the engine to stall when the throttle is closed, such as when you come to a stop.
Throttle Position Sensor (TPS): The TPS sends a signal to the engine's computer (ECU) about the position of the throttle valve. A faulty TPS can provide incorrect information to the ECU, causing the engine to stall.
MAF Sensor (Mass Airflow Sensor): The MAF sensor measures the amount of air entering the engine. A faulty MAF sensor can provide incorrect information to the ECU, which can lead to stalling.
Brake Booster: A faulty brake booster can cause a vacuum leak, affecting the engine's idle stability. Check for any hissing sounds or leaks around the brake booster.
Fuel System: A clogged fuel filter, faulty fuel pump, or leaky injector can cause a lack of fuel to the engine, leading to stalling.
EGR Valve (Exhaust Gas Recirculation): A stuck or malfunctioning EGR valve can disrupt the air-fuel mixture, causing stalling.
To diagnose the exact cause of the issue, it is recommended to perform further tests and inspections. If you're not comfortable troubleshooting and fixing the problem yourself, it's best to take the vehicle to a qualified mechanic or workshop familiar with Volvo vehicles.
