how to diagnose P0304 misfire code in Toyota Camry XV40 (2007-2011)

Toyota Camry XV80 (2025-Present)

Error Codes

2-4 hours

Time

medium

Difficulty

high

Severity

Error Code: P0304

3 min read

583 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 Toyota Camry XV40 (2007-2011). 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 battery before working on electrical systems.
•Allow engine to cool before opening any components to avoid burns.

Symptoms

•Check engine light illuminated
•Rough idle or engine shaking
•Decreased acceleration or power
•Poor fuel economy
•Engine stalling during low-speed driving
•Increased emissions

Diagnostic Steps

1
Scan for error codes using an OBD-II scanner to confirm P0304 and check for any additional codes.
2
Inspect spark plug in cylinder 4 for wear, damage, or improper gap.
3
Test ignition coil for cylinder 4 using a multimeter to check for proper resistance.
4
Check fuel injector operation for cylinder 4 by performing a balance test or using a noid light.
5
Conduct a compression test on cylinder 4 to assess mechanical integrity.
6
Inspect vacuum lines for leaks that may affect the fuel-air mixture.
7
Check for any intake manifold leaks that could cause misfire symptoms.

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
•Multimeter
•Compression gauge
•Noid light

Parts Required

•Spark plug for cylinder 4
•Ignition coil for cylinder 4 (if necessary)
•Fuel injector for cylinder 4 (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 spark plug in cylinder 4 for wear, damage, or improper gap.
3
Test ignition coil for cylinder 4 using a multimeter to check for proper resistance.
4
Check fuel injector operation for cylinder 4 by performing a balance test or using a noid light.
5
Conduct a compression test on cylinder 4 to assess mechanical integrity.
6
Inspect vacuum lines for leaks that may affect the fuel-air mixture.
7
Check for any intake manifold leaks that could cause misfire symptoms.

Solution

1. Preparation

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

2. Inspect and Replace Spark Plug

Remove the ignition coil and spark plug from cylinder 4 using a socket set.
Inspect the spark plug for signs of wear or damage; replace if necessary.
Ensure the new spark plug is gapped correctly to manufacturer specifications.
Reinstall the spark plug and ignition coil securely.

3. Test and Replace Ignition Coil (if necessary)

Disconnect the electrical connector from the ignition coil for cylinder 4.
Use a multimeter to check the primary and secondary resistance of the coil; compare with manufacturer specifications.
If the coil is faulty, replace it with a new one.
Reconnect the ignition coil connector.

4. Inspect and Test Fuel Injector

Disconnect the fuel injector connector for cylinder 4.
Use a noid light to check for proper electrical signal to the injector.
If the injector is not receiving power, trace wiring or replace the injector.
If the injector is operating, consider cleaning it or replacing it if faulty.

5. Perform Compression Test

Remove all spark plugs to facilitate cranking.
Insert a compression gauge into cylinder 4 and crank the engine.
Record the compression reading and compare it to manufacturer specifications.
If compression is low, further investigation into the engine's mechanical condition may be needed.