how to fix P0300 misfire code on BMW 5 Series G30/G31 (2017-2024)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent any electrical shorts.

2. Inspect and Replace Ignition Components

1. Visual Inspection

   • Remove the engine cover if applicable.
   • Inspect spark plugs for wear or fouling. Replace if necessary.
   • Check ignition coils for cracks or corrosion.

2. Replace Spark Plugs

   • Use a spark plug socket to remove old spark plugs.
   • Check gap specifications and replace with new spark plugs (e.g., BMW OEM parts).
   • Torque the new spark plugs to the manufacturer’s specifications (typically around 25 Nm).

3. Replace Ignition Coils

   • Disconnect the electrical connector from each ignition coil.
   • Remove the bolts securing the ignition coils and lift them out.
   • Install new ignition coils and secure them with bolts. Reconnect electrical connectors.

3. Fuel System Check

1. Fuel Pressure Test

   • Connect a fuel pressure gauge to the fuel rail.
   • Turn the ignition on (do not start the engine) and check reading; it should match manufacturer specifications (typically around 50-60 psi).
   • If pressure is low, inspect the fuel pump or fuel filter for issues.

2. Replace Fuel Filter

   • If the fuel filter is clogged, replace it according to manufacturer guidelines.
   • Ensure proper orientation and secure all connections before re-pressurizing the system.

4. Vacuum Leak Inspection

1. Visual Inspection

   • Inspect all vacuum hoses for cracks or disconnections.
   • Check intake manifold gaskets for leaks.

2. Use Smoke Tester (if available)

   • Introduce smoke into the intake system to identify leaks.
   • Repair or replace any faulty components.

5. Compression Test

1. Remove Spark Plugs

   • Remove all spark plugs to allow for easy cranking.

2. Perform Compression Test

   • Insert compression gauge into each cylinder and crank the engine.
   • Compare readings to manufacturer specifications (typically 120-180 psi).
   • Address any cylinders with noticeably lower compression.