how to fix P0304 misfire code in Tesla Outback 4th Generation (2010-2014)

Subaru Outback 4th Generation (2010-2014)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0304

4 min read

605 words

⚠️ Safety Warning

This issue requires immediate attention. If you are not experienced with automotive repairs, consult a professional mechanic. Working on critical systems can be dangerous.

Problem Statement

Learn how to diagnose and fix P0304 cylinder 4 misfire in Subaru Outback (2010-2014). Step-by-step guide with diagnostic procedures and repair instructions.

Error Code

P0304

Affected Component

Engine

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Allow the engine to cool before performing any work to avoid burns.

Symptoms

•Check engine light illuminated
•Rough idle or engine shaking
•Decreased fuel economy
•Loss of power during acceleration
•Engine stalling or hesitation
•Increased exhaust emissions

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0304 and check for any additional codes.
2
Inspect the spark plug and ignition coil for cylinder 4 for wear or damage.
3
Perform a visual inspection of the ignition wiring and connections for any signs of damage or corrosion.
4
Perform a compression test on cylinder 4 to check for internal engine issues.
5
Check fuel injector operation by performing a fuel injector balance test.
6
Inspect the intake system for vacuum leaks that may affect cylinder performance.

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
•Spark plug socket
•Torque wrench
•Multimeter
•Compression tester

Parts Required

•Spark plug
•Ignition coil (if necessary)
•Fuel injector (if necessary)

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Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0304 and check for any additional codes.
2
Inspect the spark plug and ignition coil for cylinder 4 for wear or damage.
3
Perform a visual inspection of the ignition wiring and connections for any signs of damage or corrosion.
4
Perform a compression test on cylinder 4 to check for internal engine issues.
5
Check fuel injector operation by performing a fuel injector balance test.
6
Inspect the intake system for vacuum leaks that may affect cylinder performance.

Solution

1. Preparation

Gather all necessary tools and parts.
Ensure the vehicle is parked on a level surface and the engine is cool.
Disconnect the negative battery terminal to prevent electrical short circuits.

2. Inspect and Replace Spark Plug

Tools Required: Socket set, spark plug socket, torque wrench
Remove the ignition coil from cylinder 4:
1. Disconnect the electrical connector from the ignition coil.
2. Unscrew the bolts securing the coil and carefully pull it out.
Remove the spark plug using a spark plug socket:
1. Turn counterclockwise to loosen and remove the spark plug.
Inspect the spark plug for fouling or wear. Replace if necessary with the manufacturer-recommended spark plug (e.g., NGK, Denso).
Torque the new spark plug to the specified value (typically around 13 lb-ft).

3. Inspect and Replace Ignition Coil

If the spark plug is in good condition, inspect the ignition coil:
1. Visually check for cracks, carbon tracking, or other signs of failure.
2. If defective, replace it with an OEM or quality aftermarket ignition coil designed for the Outback.
Reinstall the ignition coil:
1. Position the coil over the spark plug and secure it with the bolts.
2. Reconnect the electrical connector.

4. Check Fuel Injector

If the misfire persists, check the fuel injector for cylinder 4:
1. Use a multimeter to test the injector resistance; it should match manufacturer specifications.
2. If faulty, replace the fuel injector.
Reconnect the fuel rail and any electrical connectors.

5. Reassembly and Final Checks

Reconnect the negative battery terminal.
Ensure all components are securely installed and any tools are removed from the engine bay.