how to fix P0303 misfire code on BMW 5 Series F10/F11 (2010-2017)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to avoid electrical shorts.
• Allow the engine to cool before beginning work.

2. Inspect and Replace Ignition Components

1. Remove Engine Cover:

   • Use a socket set to remove any bolts securing the engine cover.
   • Lift the cover off and set it aside.

2. Remove Spark Plug:

   • Using a spark plug socket, remove the spark plug from cylinder 3.
   • Inspect the spark plug for signs of wear, such as fouling or excessive gap.

3. Replace Spark Plug:

   • If damaged, replace with a new spark plug that meets OEM specifications.
   • Torque the new spark plug to the manufacturer’s specified value (usually around 25 Nm).

4. Inspect Ignition Coil:

   • Disconnect the ignition coil connector.
   • Remove the coil by unscrewing it and inspect for cracks or damage.
   • If faulty, replace with a new ignition coil.

3. Check and Replace Fuel Injector

1. Remove Fuel Injector Connector:

   • Carefully disconnect the fuel injector connector for cylinder 3.

2. Remove Fuel Rail:

   • Detach the fuel rail bolts and gently pull the rail away from the intake manifold.
   • Remove the fuel injector from the rail.

3. Inspect and Replace Injector:

   • Check for clogs or leaks in the injector.
   • Replace with a new injector if necessary, ensuring proper O-ring installation.

4. Reassemble Fuel Rail:

   • Reattach the fuel rail to its mounting points and reconnect the fuel injector connectors.

4. Perform Compression Test (if required)

1. Remove Spark Plug:

   • Ensure the spark plug for cylinder 3 is removed for testing.

2. Connect Compression Tester:

   • Insert the compression tester into the spark plug hole and crank the engine for several seconds.

3. Record Compression Reading:

   • Compare the reading with manufacturer specifications, which typically range from 150-200 psi.

4. Address Low Compression:

   • If low, further investigation into valve seals or piston rings may be necessary.