how to fix P0300 misfire code in BMW 3 Series F30/F31 (2012-2019)

Solution

1. Preparation

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

2. Replace Spark Plugs

• Remove the engine cover if applicable.
• Use a socket wrench (typically 5/8") to remove the old spark plugs.
• Inspect the old plugs for signs of wear (carbon buildup, electrode wear).
• Install new spark plugs (OEM recommended) and torque them to 23 Nm (17 ft-lb).
• Reinstall the engine cover.

3. Inspect and Replace Ignition Coils

• Remove the ignition coil connectors.
• Use a socket wrench to remove the bolts securing the ignition coils.
• Pull out the ignition coils and visually inspect for damage.
• If faulty, replace with new ignition coils and reconnect the connectors.
• Ensure proper seating of the coils.

4. Check and Clean Fuel Injectors

• Disconnect the fuel pump relay and start the engine until it stalls to relieve fuel pressure.
• Remove the fuel rail and inspect fuel injectors for clogs or leaks.
• Use a fuel injector cleaner if necessary or replace injectors if damaged.
• Reinstall the fuel rail and connect the fuel pump relay.

5. Vacuum Leak Inspection

• Visually inspect all vacuum lines for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to check for leaks while the engine is running.
• Repair or replace any damaged vacuum hoses.

6. Compression Test

• Remove spark plugs again for access.
• Insert a compression gauge into each cylinder and crank the engine.
• Record the compression readings; they should be within manufacturer specifications (typically 100-200 psi).
• If readings are low, further investigation into piston rings or valves is required.