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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the engine is cool before starting work.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug gap gauge
• Remove the ignition coil by unscrewing the retaining bolts and disconnecting the electrical connector.
• Remove the spark plug using a spark plug socket.
• Inspect the old spark plug and clean the cylinder head area.
• Install a new spark plug, ensuring it is gapped to manufacturer specifications (typically 0.028-0.032 inches).
• Torque the spark plug to the manufacturer’s specification (usually around 18-22 ft-lbs).

3. Replace Ignition Coil

• Tools Required: Socket set
• If the ignition coil is faulty, replace it with a new one.
• Install the new ignition coil, ensuring it is seated properly and reattach the electrical connector.

4. Clean or Replace Fuel Injector

• Tools Required: Fuel injector cleaner, fuel line removal tools (if replacing)
• If the fuel injector is blocked or malfunctioning, clean it using a professional fuel injector cleaner or replace it with a new unit.
• Reinstall any necessary components and reconnect fuel lines ensuring there are no leaks.

5. Reassemble and Connect Battery

• Reconnect the negative battery terminal.
• Ensure all components are secured and there are no loose connections.