how to fix a misfire in my BMW 5 Series F10/F11 (2010-2017) with P0303 code

Solution

1. Preparation

• Gather tools and parts.
• Ensure the engine is cool and disconnect the negative battery terminal for safety.
• Tools Required: Socket set, torque wrench, multimeter, compression tester, fuel pressure gauge.

2. Inspect and Replace Spark Plug

• Locate the spark plug for cylinder 3.
• Use a socket wrench to remove the spark plug.
• Inspect the spark plug for wear, carbon buildup, or damage.
• If necessary, replace with a new spark plug (OEM recommended).
• Torque the new spark plug to the manufacturer’s specification (typically around 18 lb-ft).

3. Check and Replace Ignition Coil

• Remove the ignition coil from cylinder 3.
• Inspect for cracks or signs of failure.
• If defective, install a new ignition coil (OEM recommended).
• Reinstall the ignition coil and ensure it is securely connected.

4. Inspect and Test Fuel Injector

• Disconnect the fuel injector harness for cylinder 3.
• Test the injector’s resistance with a multimeter (should be within manufacturer specifications, typically around 12-16 ohms).
• If the injector is faulty, replace it with an OEM part.
• Reconnect the harness after testing or replacement.

5. Compression Test

• Remove the spark plug for cylinder 3.
• Insert the compression tester into the spark plug hole.
• Crank the engine for a few seconds to get a reading.
• Compare the reading to the manufacturer's specifications (typically around 150-200 psi).
• If compression is low, further engine diagnostics may be required.

6. Reassemble and Reconnect Battery

• Ensure all components are properly installed and secured.
• Reconnect the negative battery terminal.
• Clear any codes from the OBD-II scanner.