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

Solution

1. Preparation

• Gather necessary tools and parts.
• Park the vehicle on a flat surface and ensure the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket, dielectric grease.
• Remove the ignition coil cover (if applicable).
• Disconnect the ignition coil connector and remove the ignition coil from cylinder 1.
• Remove the spark plug using a spark plug socket.
• Inspect the old spark plug for wear and replace it with a new spark plug.
• Apply a small amount of dielectric grease to the spark plug threads.
• Torque the new spark plug to the manufacturer's specification (typically around 18-22 lb-ft).
• Reinstall the ignition coil and connector.

3. Test/Replace Ignition Coil

• Tools Required: Multimeter (for testing), replacement ignition coil (if needed).
• If the ignition coil shows signs of failure during testing, replace it with a new ignition coil.
• Ensure proper seating and connection of the replacement coil.
• Reconnect the battery terminal.

4. Inspect/Replace Fuel Injector

• Tools Required: Fuel injector removal tool, cleaning solvent (if cleaning), replacement fuel injector (if needed).
• If the injector is clogged, consider cleaning it with an appropriate solvent or replace it entirely.
• Reinstall the injector ensuring it seals properly and reconnect any electrical connectors.