How to fix the stalling problem in my Mercedes-Benz GLC X254 (2023-2024) at stop signs?

Fixing the Stalling Problem in a Mercedes-Benz GLC X254 (2023-2024) at Stop Signs

Symptoms

• Engine stalls when coming to a stop or idling.
• Dashboard warning lights may illuminate.
• Rough idling noticed before stalling.
• Difficulty restarting immediately after stalling.

Diagnostic Steps

1. Check for Error Codes

   • Use an OBD-II scanner to read error codes from the Engine Control Unit (ECU).
   • Common codes may indicate issues with the throttle body, fuel system, or ignition system.

2. Inspect Fuel System

   • Check fuel pressure using a fuel pressure gauge.
   • Look for clogged fuel filters or failing fuel injectors.
   • Ensure the fuel pump is functioning correctly.

3. Examine Air Intake System

   • Inspect the air filter for clogs.
   • Check the Mass Air Flow (MAF) sensor for dirt or damage.
   • Ensure there are no vacuum leaks in the intake system.

4. Inspect Engine Sensors

   • Check the Throttle Position Sensor (TPS) for proper operation.
   • Inspect the Idle Air Control Valve (IAC) or Electronic Throttle Control (ETC) if equipped.

5. Evaluate the Battery and Charging System

   • Ensure the battery is fully charged and in good condition.
   • Check the alternator output while the engine is running.

6. Check for Mechanical Issues

   • Inspect for any unusual noises that could indicate mechanical failures (e.g., timing belt/chain issues).
   • Verify engine mounts are intact.

Tools Required

• OBD-II Scanner
• Fuel Pressure Gauge
• Multimeter
• Basic Hand Tools (wrenches, sockets, screwdrivers)
• Vacuum Gauge
• Torque Wrench
• Cleaning Supplies (e.g., MAF cleaner, throttle body cleaner)
• Safety Equipment (gloves, goggles)

Repair Instructions

Step 1: Read and Record Error Codes

• Connect the OBD-II scanner to the vehicle’s diagnostic port.
• Follow the prompts to read the codes.
• Write down any codes for further investigation.

Step 2: Inspect Fuel System

• Using a fuel pressure gauge, attach it to the fuel rail Schrader valve.
• Turn the ignition to the ON position (do not start the engine) and note the pressure readings.
• Compare with manufacturer specifications (usually around 50-60 PSI).
• If pressure is low, check the fuel pump and filter for blockages or failures.

Step 3: Inspect Air Intake System

• Remove the air filter and inspect for dirt; replace if needed.
• Clean the MAF sensor using MAF cleaner.
• Inspect all hoses for cracks or leaks, repairing or replacing as necessary.

Step 4: Check Engine Sensors

• Use a multimeter to test the TPS:
  • Disconnect the TPS connector.
  • Measure resistance across the terminals while moving the throttle. It should show a smooth change in resistance.
• If faulty, replace the TPS.
• For the IAC, clean or replace if it’s not functioning correctly.

Step 5: Evaluate Battery and Charging System

• Use a multimeter to measure battery voltage (should be around 12.6V when off, 13.7-14.7V when running).
• If readings are outside the range, check for alternator or battery issues.

Step 6: Mechanical Inspection

• Listen for any unusual noises during idle that could indicate engine issues.
• Inspect engine mounts; replace if any are cracked or broken.

Step 7: Final Checks and Test Drive

• Once repairs are made, clear any error codes using the OBD-II scanner.
• Start the engine and let it idle to ensure it operates smoothly.
• Take the vehicle for a test drive, stopping at stop signs to verify that the stalling issue is resolved.

Conclusion

If after these steps the stalling issue persists, it may be advisable to consult with a qualified Mercedes-Benz technician or authorized service center for further diagnostics, as newer models may have complex electronic components that require specialized tools and knowledge.