how to fix P0302 misfire code in 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 Spark Plug

• Remove the engine cover if required using a socket set.
• Disconnect the ignition coil connector and remove the bolt holding the ignition coil.
• Carefully pull the ignition coil out of the cylinder head.
• Remove the spark plug using a spark plug socket, ensuring it does not drop debris into the cylinder.
• Install the new spark plug, ensuring it is torqued to the manufacturer’s specifications (typically around 18 lb-ft).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Replace Ignition Coil (if necessary)

• If the ignition coil was found to be faulty during diagnostics, replace it.
• Follow the same steps as for the spark plug to remove the ignition coil and install a new one.

4. Clean or Replace Fuel Injector

• If the fuel injector is faulty or clogged, remove it by disconnecting the electrical connector and fuel line.
• Use a fuel injector cleaner to clean the injector or replace it with a new one if necessary.
• Reinstall the fuel injector and ensure all connections are secure.

5. Compression Test (if necessary)

• If compression is low, remove the spark plug and perform a compression test.
• Use a compression gauge to check cylinder pressure; refer to manufacturer specifications for acceptable pressure range.
• If pressure is low, further investigation may be needed to check for valve issues or head gasket failure.