how to fix code P0304 on BMW 3 Series F30/F31 (2012-2019)?

BMW 3 Series F30/F31 (2012-2019)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

Error Code: P0304

4 min read

624 words

Problem Statement

Code P0304 indicates a misfire detected in cylinder 4 of a BMW 3 Series F30/F31 (2012-2019). This misfire can lead to rough engine performance, increased emissions, and potential

Error Code

P0304

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical components.
•Allow the engine to cool before removing spark plugs or working on the ignition system.

Symptoms

•Check engine light illuminated
•Rough idle or engine shaking
•Loss of power during acceleration
•Decreased fuel economy
•Unusual engine noises (e.g., popping or backfiring)
•Increased exhaust emissions

Diagnostic Steps

1
Scan the vehicle's OBD-II system for additional error codes that may indicate other issues.
2
Inspect the ignition coil and spark plug for cylinder 4 for wear or damage.
3
Check the fuel injector operation for cylinder 4 using a fuel injector tester.
4
Perform a compression test on cylinder 4 to determine engine health.
5
Inspect vacuum lines and intake manifold gaskets for leaks that could affect cylinder performance.
6
Use a multimeter to test the resistance of the ignition coil.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•OBD-II scanner
•Socket set
•Torque wrench
•Spark plug socket
•Multimeter
•Compression gauge
•Fuel injector tester

Parts Required

•Spark plug (specific to the vehicle)
•Ignition coil (if faulty)
•Fuel injector (if faulty)

Related Faults

Share this solution

Comments

No comments yet

Be the first to share your thoughts

Back to Generation

Diagnostic Steps

1
Scan the vehicle's OBD-II system for additional error codes that may indicate other issues.
2
Inspect the ignition coil and spark plug for cylinder 4 for wear or damage.
3
Check the fuel injector operation for cylinder 4 using a fuel injector tester.
4
Perform a compression test on cylinder 4 to determine engine health.
5
Inspect vacuum lines and intake manifold gaskets for leaks that could affect cylinder performance.
6
Use a multimeter to test the resistance of the ignition coil.

Solution

1. Preparation

Gather tools and parts required for the repair.
Disconnect the negative terminal of the battery to prevent electrical shorts.
Allow the engine to cool if it has been running.

2. Inspect and Replace Spark Plug

Sub-steps:
1. Remove the engine cover (if applicable) using a socket set.
2. Disconnect the ignition coil connector on cylinder 4.
3. Remove the ignition coil using a socket wrench.
4. Remove the spark plug from cylinder 4 with a spark plug socket.
5. Inspect the spark plug for wear, carbon buildup, or damage. Replace if necessary.
6. Install the new spark plug, torque to manufacturer specifications (typically around 23 Nm or 17 ft-lbs).
7. Reinstall the ignition coil and reconnect the connector.

3. Inspect and Replace Ignition Coil

Sub-steps:
1. If the spark plug appears normal, inspect the ignition coil for damage.
2. Test the ignition coil with a multimeter; replace if resistance is out of spec (typically 0.5 to 1.5 ohms).
3. To replace, simply remove the old ignition coil and install the new one, ensuring it is seated properly.

4. Inspect Fuel Injector

Sub-steps:
1. Remove the fuel rail if necessary to access the injector for cylinder 4.
2. Disconnect the fuel injector connector.
3. Test the injector operation using a fuel injector tester.
4. Replace the injector if it is not operating correctly, ensuring to replace any O-rings.

5. Perform Compression Test

Sub-steps:
1. Remove the spark plug from cylinder 4.
2. Install a compression gauge into the spark plug hole.
3. Crank the engine and record the compression reading. Compare it to specifications (typically 140-200 psi).
4. If compression is low, further diagnosis is required, which may include checking valves or piston rings.