how to fix P0302 misfire code in Alfa Romeo Giulia 952 (2016-Present)

Symptoms

• Check engine light illuminated
• Rough idle or engine vibrations
• Loss of power during acceleration
• Increased fuel consumption
• Engine stalling at idle
• Unusual exhaust emissions (e.g., black smoke)

Diagnostic Steps

1. Scan the vehicle’s onboard computer using an OBD-II scanner to confirm the P0302 code and check for any additional trouble codes.
2. Inspect the ignition coil and spark plug for cylinder 2 for signs of wear, damage, or carbon buildup.
3. Check for vacuum leaks around the intake manifold and hoses that could affect cylinder 2's air-fuel mixture.
4. Perform a compression test on cylinder 2 to ensure proper compression is present.
5. Examine fuel injector function for cylinder 2 by performing a resistance test and checking for proper spray pattern.
6. Inspect the wiring and connectors related to the ignition system and fuel injector for signs of damage or corrosion.

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the parking brake is engaged.
• Disconnect the negative battery terminal to prevent any electrical issues during the repair.

2. Replace Spark Plug

1. Remove the engine cover (if applicable) using a socket set.
2. Disconnect the ignition coil connector from cylinder 2.
3. Remove the ignition coil by unscrewing it from the cylinder head.
4. Unscrew the spark plug using a spark plug socket and ratchet.
5. Inspect the old spark plug; if it shows signs of wear (e.g., excessive gap, carbon deposits), replace it with a new one, ensuring it matches OEM specifications.
6. Torque the new spark plug to the manufacturer's specifications (typically around 13-15 lb-ft).
7. Reinstall the ignition coil and reconnect the connector.

3. Inspect and Replace Ignition Coil

1. If the spark plug replacement does not resolve the misfire, proceed to inspect the ignition coil.
2. Remove the ignition coil from cylinder 2 as previously described.
3. Test the ignition coil with a multimeter according to the manufacturer’s specifications for primary and secondary resistance.
4. If the coil is faulty, replace it with a new OEM ignition coil.
5. Reinstall the ignition coil and reconnect the connector securely.

4. Check Fuel Injector

1. If misfire persists, inspect the fuel injector for cylinder 2.
2. Remove the fuel rail (after relieving fuel pressure) according to the manufacturer’s instructions.
3. Test the fuel injector resistance using a multimeter (should be around 12-16 ohms).
4. If the injector is faulty, replace it with a new one.
5. Reinstall the fuel rail and ensure all connections are secure.

5. Reassemble and Test

1. Reattach any components removed during the repair (engine cover, connectors, etc.).
2. Reconnect the negative battery terminal.
3. Start the engine and let it idle to check for improvement in performance.