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

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, fuel pressure gauge, compression tester, multimeter, noid light.
• Disconnect the negative terminal of the battery to prevent electrical shock.

2. Inspect and Replace Ignition Components

1. Remove Engine Cover (if applicable)

   • Use a socket set to remove bolts securing the engine cover.
   • Carefully lift the cover and set it aside.

2. Inspect Spark Plugs

   • Remove spark plug boots by gently twisting and pulling.
   • Use a spark plug socket to remove each spark plug.
   • Inspect for wear, carbon buildup, or damage. Replace if necessary.

3. Replace Ignition Coils

   • Unplug the electrical connector from each ignition coil.
   • Remove bolts securing the coils and lift them out.
   • Install new ignition coils by reversing the removal steps, ensuring they are seated correctly.

3. Check and Adjust Fuel Delivery

1. Check Fuel Pressure

   • Connect a fuel pressure gauge to the fuel rail service port.
   • Turn the ignition on (do not start the engine) and read the pressure. It should meet manufacturer specifications.
   • If pressure is low, replace the fuel pump or check the fuel filter.

2. Inspect and Test Fuel Injectors

   • Use a noid light to check the injector signal while cranking the engine.
   • Replace any faulty injectors as necessary.

4. Inspect for Vacuum Leaks

1. Check for Leaks
   • Visually inspect all vacuum hoses for cracks or disconnections.
   • Use a smoke tester if available to identify leaks in the intake system.
   • Replace any damaged hoses or seals.

5. Perform Compression Test

1. Check Compression
   • Remove spark plugs again for access.
   • Insert compression tester into the spark plug holes and crank the engine.
   • Record the readings; they should be within manufacturer specifications.
   • Address any low compression issues by diagnosing further (e.g., valve seals, head gasket).