how to fix P0304 code in Honda Accord 9th Generation (2013-2017)

Honda Accord Eleventh Generation (2023-present)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0304

3 min read

598 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 Honda Accord 9th Generation. 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 components.
•Allow the engine to cool before opening any components to avoid burns.

Symptoms

•Check engine light illuminated
•Rough idle or engine shaking
•Decreased engine performance or power
•Poor fuel economy
•Increased exhaust emissions
•Possible engine stalling

Diagnostic Steps

1
Scan the vehicle's onboard computer with an OBD-II scanner to confirm the P0304 code and check for any related codes.
2
Inspect spark plugs in cylinder 4 for wear or damage, and check the condition of the other spark plugs.
3
Check the ignition coil for cylinder 4 by performing a resistance test and ensuring proper functionality.
4
Inspect the fuel injector for cylinder 4 to ensure it is delivering fuel correctly.
5
Conduct a compression test on cylinder 4 to assess the integrity of the piston rings and valves.
6
Check for vacuum leaks around the intake manifold and hoses that could 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
•Torque wrench
•Multimeter
•Compression tester
•Spark plug socket

Parts Required

•Spark plug (for cylinder 4)
•Ignition coil (if necessary)
•Fuel injector (if necessary)

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Diagnostic Steps

1
Scan the vehicle's onboard computer with an OBD-II scanner to confirm the P0304 code and check for any related codes.
2
Inspect spark plugs in cylinder 4 for wear or damage, and check the condition of the other spark plugs.
3
Check the ignition coil for cylinder 4 by performing a resistance test and ensuring proper functionality.
4
Inspect the fuel injector for cylinder 4 to ensure it is delivering fuel correctly.
5
Conduct a compression test on cylinder 4 to assess the integrity of the piston rings and valves.
6
Check for vacuum leaks around the intake manifold and hoses that could affect cylinder performance.

Solution

1. Preparation

Gather the necessary tools and parts.
Disconnect the negative terminal of the battery to ensure safety.
Allow the engine to cool before proceeding.

2. Inspect and Replace Spark Plug

Remove the ignition coil from cylinder 4 using a socket set.
Extract the spark plug from cylinder 4 with a spark plug socket.
- Tools Required: Spark plug socket, ratchet, torque wrench.
Inspect the spark plug for signs of wear (e.g., carbon buildup, burning).
If defective, replace the spark plug with a new one, ensuring it is gapped correctly to manufacturer specifications (typically around 0.043 inches for Honda).
Reinstall the ignition coil and reconnect the electrical connector.

3. Test and Replace Ignition Coil (if necessary)

If the spark plug is fine, test the ignition coil using a multimeter to check for proper resistance (consult service manual for specific values).
If the ignition coil is faulty, replace it with a new one.
- Tools Required: Socket set, torque wrench.
Reconnect the electrical connection and ensure it is securely fastened.

4. Inspect Fuel Injector

Remove the fuel rail to access the fuel injector for cylinder 4.
- Tools Required: Socket set, fuel injector puller if necessary.
Check the injector for clogs or electrical issues.
Clean or replace the injector if necessary, ensuring it seats correctly when reinstalled.

5. Conduct Compression Test

Perform a compression test on cylinder 4.
If compression is below specification (consult service manual for exact values), further investigation into engine internals may be required (valve seals, piston rings).