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

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool before starting work.

2. Replace Spark Plug

• Remove the engine cover if necessary.
• Use a socket and ratchet to remove the spark plug from cylinder 1.
  • Torque specification: 18 lb-ft (25 Nm) when reinstalling.
• Inspect the old spark plug for signs of wear or damage.
• Install a new spark plug, ensuring proper gap settings as per manufacturer specifications.

3. Inspect/Replace Ignition Coil

• Disconnect the wiring harness from the ignition coil on cylinder 1.
• Remove the ignition coil using a socket and ratchet.
• Inspect the ignition coil for cracks or signs of arcing.
• If necessary, replace with a new ignition coil, ensuring it is seated properly.

4. Test/Replace Fuel Injector

• Disconnect the fuel injector connector for cylinder 1.
• Use a noid light to check for injector pulse while cranking the engine.
• If no signal is detected, check the wiring or replace the injector with a new one.
• If the injector is defective, replace it and ensure it is securely connected.

5. Perform Compression Test

• Remove the spark plug from cylinder 1.
• Insert a compression gauge into the spark plug hole.
• Crank the engine and record the compression reading.
  • Acceptable range: 120-200 psi depending on the engine specifications.
• If compression is below the acceptable range, further investigation may be required (potential valve or piston damage).

6. Check for Vacuum Leaks

• Inspect all vacuum lines and gaskets around the intake manifold for signs of leaks.
• Use a smoke machine or carburetor cleaner to identify leaks while the engine is running.
• Repair or replace any damaged hoses or gaskets.