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

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to ensure safety.

2. Replace Ignition Coil

1. Locate the ignition coil for cylinder 1.
2. Disconnect the electrical connector from the ignition coil.
3. Remove the retaining bolt(s) securing the ignition coil.
4. Pull out the ignition coil from the spark plug tube.
5. Install the new ignition coil by reversing the removal steps.

3. Replace Spark Plug

1. Remove the ignition coil if not already done.
2. Use a spark plug socket and ratchet to remove the old spark plug.
3. Inspect the spark plug for wear; if necessary, clean the spark plug hole.
4. Check the gap on the new spark plug with a feeler gauge, adjusting as needed.
5. Install the new spark plug by hand, then torque to the manufacturer’s specifications (usually around 13 lb-ft).
6. Reattach the ignition coil.

4. Inspect and Clean Fuel Injector (if necessary)

1. Disconnect the fuel injector connector for cylinder 1.
2. Remove the fuel rail (if required) to access the injector.
3. Clean the fuel injector using an appropriate cleaner or replace if faulty.
4. Reassemble the injector and fuel rail, ensuring seals are properly seated.

5. Check Compression (if necessary)

1. Remove the spark plug from cylinder 1.
2. Attach a compression gauge to the spark plug hole.
3. Crank the engine and record the compression reading.
4. Compare the reading with manufacturer specifications to determine if further internal engine work is necessary.