how to fix my BMW 5 Series G30/G31 (2017-2024) with a P0301 misfire code

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, spark plug socket, multimeter, compression tester, fuel injector cleaner.
• Disconnect the negative battery terminal to ensure safety while working on electrical components.

2. Inspect and Replace Spark Plug

• Remove the engine cover if applicable.
• Use a spark plug socket to remove the spark plug from cylinder 1.
• Inspect the spark plug for signs of wear, such as carbon buildup or excessive wear.
• If necessary, replace the spark plug with a new one that meets OEM specifications (typically NGK or Bosch).
• Torque the new spark plug to the manufacturer's specified value (usually around 18-22 lb-ft).

3. Check and Replace Ignition Coil

• Disconnect the electrical connector from the ignition coil on cylinder 1.
• Remove the ignition coil using a socket and pull it straight out.
• Test the ignition coil with a multimeter to check for proper resistance values (typically 0.5-1.5 ohms for primary resistance).
• If faulty, replace the ignition coil with a new one that matches OEM specifications.
• Reinstall the ignition coil and reconnect the electrical connector.

4. Perform Compression Test

• Remove the spark plug from cylinder 1 and install the compression tester.
• Crank the engine and record the compression reading. Compare to the manufacturer's specifications (usually around 180-220 psi).
• If the compression is low, further diagnosis may be needed (valve issues, head gasket failure).

5. Inspect and Clean Fuel Injector

• Remove the fuel injector for cylinder 1 by detaching the fuel rail if necessary.
• Inspect the injector for clogs or damage.
• Clean the injector using a specialized fuel injector cleaner or replace it if necessary.
• Reinstall the injector and ensure all connections are secure.

6. Check for Vacuum Leaks

• Inspect vacuum lines and connections around the intake manifold for leaks.
• Use a smoke machine or carburetor cleaner to check for leaks while the engine is running.
• Repair or replace any leaking components.