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Engine-Codes – Honda – P0304 Honda

P0304 Honda Code - No. 4 Cylinder Misfire Detected

Quick Answer

The P0304 diagnostic trouble code for Honda vehicles indicates that a misfire has been detected in the No. Common causes include Faulty spark plug, Faulty ignition coil, Clogged fuel injector. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means
P0304 Honda indicates No. 4 Cylinder Misfire Detected.
Common causes
Common causes include Faulty spark plug, Faulty ignition coil, Clogged fuel injector.
Severity
High - diagnose this code as soon as possible.
Can I drive?
Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
What is this?
Table of contents Created and updated by William Orellana on Sep 07, 2024
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Code P0304 Honda Description

The P0304 diagnostic trouble code for Honda vehicles indicates that a misfire has been detected in the No. 4 cylinder of the engine. This means that the cylinder is not firing properly, which can lead to a range of issues affecting the vehicle's performance. When a cylinder misfires, it can cause a rough idle, hesitation or stumbling during acceleration, loss of power, decreased fuel efficiency, and increased emissions.

OBDII Code P0304 Honda - No. 4 Cylinder Misfire Detected
P0304 Honda Code - No. 4 Cylinder Misfire Detected

Common Causes of P0304 Honda

  1. Faulty spark plug
  2. Faulty ignition coil
  3. Clogged fuel injector
  4. Low fuel pressure
  5. Vacuum leaks

Symptoms of P0304 Honda

  1. Rough idle
  2. Hesitation or stumbling during acceleration
  3. Loss of power
  4. Decreased fuel efficiency
  5. Increased emissions

How to Fix P0304 Honda

  1. Diagnose the specific cause of the misfire by using a scan tool to identify the No. 4 cylinder misfire code.
  2. Inspect and test the spark plug, ignition coil, and spark plug wire for proper functioning. Replace any faulty components.
  3. Check the fuel injector for clogs or leaks, and test the fuel pressure to ensure it is within the manufacturer's specifications. Address any fuel system issues accordingly.
  4. Inspect the engine for vacuum leaks and repair or replace any damaged hoses or components.
  5. Clear the diagnostic trouble code and test drive the vehicle to ensure the misfire issue has been resolved.

Cost to Fix P0304 Honda

The cost of repairing a No. 4 cylinder misfire in a Honda vehicle can vary depending on the specific cause of the issue and the parts and labor required for the repair. On average, the cost of parts for this repair could range from $50 to $200, while labor costs could range from $100 to $300. Overall, the total repair cost for this issue could range from $150 to $500. It is important to note that these are rough estimates, and actual costs may vary based on factors such as location, vehicle make and model, and the severity of the issue. Additionally, the specific diagnosis time and labor rates at auto repair shops can also impact the overall cost of the repair. It is recommended to obtain quotes from multiple auto repair shops to ensure a competitive price for the repair.

What does this mean?

Tech Notes for P0304 Honda

The P0304 code means that cylinder #4 is misfiring or is randomly misfiring. Start by checking for intake leaks and if no leaks are found the next step is to replace the spark plugs on cylinder #4. If the problem persists more tests need to be done to diagnose the problem, see "Possible Causes".

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Information for Specific Honda Models

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0304 Honda Code

1. What are common symptoms of OBDII code P0304 in a Honda?

Symptoms include engine misfire, loss of power, rough idling, and potential engine vibration.

2. What are the typical causes of a No. 4 cylinder misfire detected in a Honda?

Common causes include faulty spark plugs, ignition coils, fuel injectors, vacuum leaks, or low compression in the No. 4 cylinder.

3. How can I diagnose the source of the misfire in the No. 4 cylinder of my Honda?

You can diagnose the issue by performing a visual inspection of spark plugs, checking ignition coils, testing fuel injectors, and conducting a compression test on the affected cylinder.

4. Can driving with a P0304 code harm my Honda's engine?

Continued driving with a misfire can potentially damage the catalytic converter and other engine components, so it's advisable to address the issue promptly.

5. Are there any simple fixes I can try before taking my Honda to a mechanic for a P0304 code?

You can start by checking and replacing the spark plugs, inspecting the ignition coil for damage, and ensuring there are no vacuum leaks around the No. 4 cylinder.

6. How much does it typically cost to repair a No. 4 cylinder misfire in a Honda?

The cost can vary depending on the exact cause of the misfire, but it may range from $100 to $500 for parts and labor.

7. Can a dirty fuel system cause a No. 4 cylinder misfire in a Honda triggering code P0304?

Yes, a dirty fuel system can lead to poor fuel delivery to the No. 4 cylinder, causing a misfire and triggering the P0304 code.

8. Is it safe to continue driving my Honda if the check engine light is on due to code P0304?

It is not recommended to drive the vehicle extensively with a misfire issue as it can lead to further damage and potentially unsafe driving conditions.

9. Can extreme weather conditions affect the occurrence of a No. 4 cylinder misfire in a Honda?

Yes, extreme temperatures or humidity levels can impact the ignition system and fuel delivery, potentially leading to a misfire in the No. 4 cylinder.

10. How often should I perform maintenance to prevent a No. 4 cylinder misfire in my Honda?

Regular maintenance, including timely spark plug replacements, fuel system cleaning, and periodic checks of ignition components, can help prevent misfire issues in your Honda.

Discuss the causes and fixes for P0304 Honda OBDII Code

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  • rough idle at start up, goes away when engine warms up.

    Reply to Comment

  • What model and year is your Honda?

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  • i have a Honda crv is misfiring in the number four cylinder,once it has heaten up t goes away

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  • If the spark plugs are OK, you should perform a compression test. May have a blown head gasket.

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  • I have a 2000 civic ex my compression on the 4th cylinder is about 30 what dou you think it is?

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  • More than likely a head gasket.

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  • P0304 cylinder 4 random misfire. Replaced ignition wires, plugs, dristributor cap and rotor. Ran injector cleaner through engine and still having engine hesitation sometimes. Still reading code p0304. What do I do next swap ingectors?

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  • What model and year is your Honda? You may have to adjust the valves.

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  • Hi, I keep getting the code P0304, P0301,P0303 and random misfire. I have a Honda Odyssey 2006, 3.5. I already replaced the spark plugs and the fuel injectors. What could it be?

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  • Valve adjustment it's probably the most likely cause of the problem.

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  • Driving a Honda Insight from 2012, and this error code was the cause of a complete engine failure due to a faulty (overheated) spark plug. Was driving for an hour on the highway before a rather noticeable pop caused a complete loss of power (automatic car, went to neutral). After cooling down, error disappeared but engine did not run anymore. Just got a call from the mechanics that they had to open up the motor block to assess the damage, since parts of the spark plug seem to have gotten missing...

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  • MOST RANDOM NOT HARD BMISS FIRE ON MOST HONDAS ARE PLUGS OR VALVE ADJUST MENT. IF YOU LOOK AT (MAP) SENSOR IT SHOULD BE AROUND .88 MUCH HIGER READINGS THE VALES ARE OUT MOST LIKELY. THE EXAUST VALVES GET TIGHT AND HANG OPEN CAUSING THE MISS FIRE.

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