how to fix P0301 misfire code in BMW 3 Series E90/E91 (2005-2012)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket
• Remove the ignition coil by unscrewing the retaining bolts and gently pulling it out.
• Unscrew the spark plug using the spark plug socket and inspect it. Replace if worn or fouled.
• Install the new spark plug and torque it to the manufacturer’s specifications (usually around 18-22 Nm).
• Reinstall the ignition coil, ensuring it is seated properly and secure.

3. Inspect and Replace Ignition Coil (if necessary)

• If the ignition coil appears damaged or if misfires persist, replace it.
• Tools Required: Socket set
• Remove the old ignition coil and replace it with a new one, ensuring a snug fit.

4. Check and Replace Fuel Injector (if necessary)

• Disconnect the fuel line and electrical connector from the fuel injector.
• Remove the injector from the rail and inspect for clogs or damage.
• Replace with a new injector if needed, ensuring it is properly seated and connected.

5. Perform Compression Test

• Tools Required: Compression tester
• Remove the spark plug and install the compression tester into cylinder 1.
• Crank the engine to check compression levels; refer to specifications (usually 130-200 psi).
• If compression is low, further diagnostics may be needed for valve or piston issues.