my Alfa Romeo Giulia 952 (2016-Present) has a rough idle when cold

Symptoms

• Rough idle when the engine is cold
• Engine stalling when coming to a stop
• Increased fuel consumption
• Check engine light illuminated
• Unusual engine noises (e.g., knocking or misfiring)

Diagnostic Steps

1. Scan for error codes using an OBD-II scanner to identify any fault codes related to the engine.
2. Inspect the air intake system for any leaks or obstructions.
3. Check the condition of the spark plugs and ignition coils for wear or damage.
4. Test the fuel pressure to ensure it meets specifications.
5. Examine the throttle body for carbon buildup or malfunction.
6. Monitor the engine coolant temperature sensor readings for accuracy.

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the vehicle.
• Allow the engine to cool if it has been running.

2. Inspect and Replace Spark Plugs

• Remove the engine cover if applicable.
• Using a socket wrench, carefully unbolt and remove the spark plug wires or coils.
• Use a spark plug socket to remove old spark plugs.
• Inspect the plugs for wear; replace them with new ones if necessary (specifications: NGK or OEM equivalent, gap to manufacturer specs).
• Reinstall new spark plugs and reconnect wires or coils securely.

3. Clean Throttle Body

• Remove the air intake duct to access the throttle body.
• Use throttle body cleaner and a soft cloth to clean the throttle plate and surrounding areas.
• Ensure that the throttle plate operates smoothly without sticking.
• Reattach the air intake duct securely.

4. Inspect Air Intake System

• Visually check for any cracks or leaks in the intake hoses and connectors.
• Replace any damaged hoses or clamps as necessary.
• Ensure the air filter is clean; replace if dirty.

5. Check Fuel Pressure

• Connect a fuel pressure gauge to the fuel rail.
• Turn the ignition key to the "on" position (do not start) and check the pressure reading against the specifications.
• If the pressure is low, inspect the fuel pump and filter for issues and replace if necessary.