how to fix a Ford Mustang S550 (2015-2023) that stalls at stoplights

Solution

1. Preparation

• Ensure the vehicle is parked on a level surface and the engine is turned off.
• Disconnect the negative battery terminal to prevent electrical shock.

2. Inspect and Clean Idle Air Control Valve

• Tools Required: Torx screwdriver, throttle body cleaner, clean cloth
• Remove the IAC valve from the throttle body.
• Inspect the valve for carbon buildup.
• Clean the valve and its port with throttle body cleaner and a cloth.
• Reinstall the IAC valve and reconnect the electrical connector.

3. Inspect Vacuum Lines

• Tools Required: Visual inspection tools (flashlight), vacuum gauge
• Visually inspect all vacuum lines for cracks, breaks, or disconnections.
• Use a vacuum gauge to test the integrity of the vacuum system.
• Replace any damaged vacuum lines found during inspection.

4. Test Fuel Pressure

• Tools Required: Fuel pressure gauge
• Locate the fuel pressure test port on the fuel rail.
• Connect the fuel pressure gauge and turn the ignition to the "ON" position (do not start the engine) to check pressure readings.
• Compare the readings to the manufacturer's specifications (typically around 40-60 psi).
• Address any issues found, such as a failing fuel pump or clogged fuel filter.

5. Clean Throttle Body

• Tools Required: Throttle body cleaner, clean cloth, socket set
• Remove the throttle body from the intake manifold.
• Clean the inside of the throttle body with throttle body cleaner and a cloth, ensuring no debris remains.
• Reinstall the throttle body with new gaskets if necessary, following the torque specifications for the bolts.

6. Verify Electrical System

• Tools Required: Multimeter
• Check the battery voltage and alternator output.
• Ensure the battery voltage is above 12.6 volts and the alternator is supplying 13.5-14.5 volts while the engine is running.
• Replace the battery or alternator if either is found to be faulty.