how to fix P0304 code in my BMW X3 F25 (2011-2018)

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter.
• Disconnect the negative battery terminal to ensure safety during repairs.

2. Replace Ignition Coil

• Remove the engine cover if applicable.
• Locate the ignition coil for cylinder 4 (refer to the engine layout).
• Disconnect the wiring harness from the ignition coil.
• Remove the ignition coil by unscrewing the bolts (torque values: typically 10-12 Nm).
• Install the new ignition coil by reversing the removal steps and ensure it is securely connected.

3. Replace Spark Plug

• Access the spark plug in cylinder 4 using a spark plug socket.
• Remove the old spark plug and inspect for damage or excessive wear.
• Check and adjust the gap on the new spark plug according to manufacturer specifications (typically 0.7-0.8 mm for BMW).
• Install the new spark plug and torque to the recommended value (usually 23-30 Nm).

4. Inspect/Replace Fuel Injector

• Disconnect the fuel injector electrical connector for cylinder 4.
• Remove the fuel rail if necessary to access the injector (follow manufacturer instructions).
• Inspect the fuel injector for clogs or leaks; replace if necessary.
• Reinstall the fuel injector and ensure it's properly seated.

5. Compression Test

• Remove the spark plug from cylinder 4.
• Insert the compression tester into the spark plug hole.
• Crank the engine and observe the compression reading; it should be within the manufacturer's specified range (typically 120-200 psi).
• If compression is low, further investigation into internal engine issues may be required.