how to fix P0300 random misfire code in my BMW 5 Series F10/F11 (2010-2017)?

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool down before starting work.

2. Replace Spark Plugs

• Remove the engine cover if applicable.
• Use a socket set to remove the spark plug boots.
• Unscrew the spark plugs using a spark plug socket and ratchet.
• Inspect the old spark plugs for signs of wear or fouling.
• Install new spark plugs by hand tightening and then using a torque wrench to tighten to manufacturer specifications (typically around 20 Nm).
• Reconnect the ignition coil boots securely.

3. Check and Replace Ignition Coils

• If symptoms persist after spark plug replacement, remove the ignition coils by unscrewing the retaining bolts.
• Inspect each ignition coil for damage or cracks.
• Replace any defective coils with new ones, ensuring they are seated properly.

4. Inspect Fuel Injectors

• If misfires continue, check fuel injector operation by removing the fuel rail.
• Use a fuel pressure gauge to ensure proper fuel pressure (typically around 3.5 bar).
• Clean or replace clogged injectors as necessary.

5. Check for Vacuum Leaks

• Inspect all vacuum hoses and connections for cracks or disconnections.
• Use a smoke machine or carburetor cleaner to identify leaks around the intake manifold.
• Repair or replace any damaged hoses.

6. Compression Test (if required)

• Remove spark plugs and connect a compression tester to each cylinder.
• Crank the engine and record compression readings for each cylinder. Normal readings should be between 12-16 bar.
• If any cylinder shows low compression, further inspection may be needed for valves or piston rings.