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Engine-Codes – Ford – P0304 Ford

P0304 Ford Code - Cylinder 4 Misfire Detected

Quick Answer

When the diagnostic trouble code P0304 appears on a Ford vehicle, it indicates that a misfire has been detected in cylinder 4 of the engine. Common causes include Faulty spark plug or ignition coil, Clogged fuel injector, Vacuum leak. 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 Ford indicates Cylinder 4 Misfire Detected.
Common causes
Common causes include Faulty spark plug or ignition coil, Clogged fuel injector, Vacuum leak.
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 Aug 19, 2024
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Code P0304 Ford Description

When the diagnostic trouble code P0304 appears on a Ford vehicle, it indicates that a misfire has been detected in cylinder 4 of the engine. This means that the cylinder is not firing properly, leading to a lack of power, rough idle, and potentially increased emissions. A misfire can be caused by a variety of factors, including issues with the ignition system, fuel system, or engine mechanical problems. If left unaddressed, a misfiring cylinder can lead to decreased fuel efficiency, engine damage, and overall poor performance of the vehicle.

OBDII Code P0304 Ford - Cylinder 4 Misfire Detected
P0304 Ford Code - Cylinder 4 Misfire Detected

Common Causes of P0304 Ford

  1. Faulty spark plug or ignition coil
  2. Clogged fuel injector
  3. Vacuum leak
  4. Low compression in cylinder 4
  5. Engine timing issues

Symptoms of P0304 Ford

  1. Rough idle
  2. Loss of power
  3. Engine vibration
  4. Increased fuel consumption
  5. Check Engine Light illuminated

How to Fix P0304 Ford

  1. Use a scan tool to identify the specific cylinder causing the misfire (cylinder 4 in this case).
  2. Check and replace spark plugs and ignition coils if necessary.
  3. Inspect and clean fuel injectors.
  4. Perform a compression test to check for low compression in cylinder 4.
  5. Verify and adjust engine timing if needed.

Cost to Fix P0304 Ford

The typical repair costs for addressing a cylinder 4 misfire on a Ford vehicle can range from $100 to $500, depending on the specific cause of the issue and the parts needed for repair. Additional costs may be incurred for diagnostic testing and labor. It's important to consult with a qualified mechanic or auto repair shop to get an accurate estimate based on the vehicle's make and model, as well as the extent of the repairs needed. Labor rates can vary, so it's advisable to inquire about pricing before proceeding with the repair.

What does this mean?

Tech Notes for P0304 Ford

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" for the most common problems.

There is a Factory Service Bulletin for the 2011 Ford Mustang:
2011 Ford Mustang Factory Service Bulletin OBDII Code P0304
The Factory Service Bulletin recommends reprogramming the Powertrain Control Module (PCM) to resolve the problem.













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Information for Specific Ford 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 Ford Code

1. What does OBDII code P0304 mean on a Ford vehicle?

P0304 indicates that the engine's computer has detected a misfire specifically in cylinder 4.

2. What are the symptoms of a P0304 code on a Ford?

Symptoms may include rough idling, reduced engine performance, poor fuel economy, engine shaking, and the Check Engine Light turning on.

3. What causes a P0304 code on a Ford?

Common causes include a faulty spark plug, a damaged ignition coil, a clogged fuel injector, low cylinder compression, or a vacuum leak near cylinder 4.

4. Can I drive my Ford with a P0304 code?

Driving with a P0304 code is not recommended, as it can lead to further engine damage, including potential catalytic converter failure.

5. How do I diagnose a P0304 code on my Ford?

Start by inspecting the spark plug, ignition coil, and fuel injector for cylinder 4. Also, check for vacuum leaks, low compression, or wiring issues.

6. How can I fix a P0304 code on a Ford?

Repairs may include replacing the spark plug or ignition coil for cylinder 4, cleaning or replacing the fuel injector, fixing vacuum leaks, or addressing low compression issues.

7. How much does it cost to repair a P0304 code on a Ford?

The cost depends on the issue. Replacing a spark plug or ignition coil can cost $50–$300, while more complex repairs like addressing low compression may cost significantly more.

8. Can a dirty air filter cause a P0304 code on a Ford?

While unlikely, a severely dirty air filter can contribute to air/fuel mixture issues, which might exacerbate a misfire.

9. Will clearing the P0304 code fix the problem?

Clearing the code will turn off the Check Engine Light temporarily, but the underlying issue causing the misfire must be resolved to prevent the code from returning.

10. How can I prevent a P0304 code on my Ford in the future?

Regular maintenance, such as replacing spark plugs, inspecting ignition coils, and cleaning fuel injectors, can help prevent misfires and the P0304 code.

Discuss the causes and fixes for P0304 Ford OBDII Code

Submit a New Comment

  • Low compression on cylinder 4. Had replaced plug and wires 3 times. Help.

    Reply to Comment

  • What model and year is your Ford? if you did a compression test and had low compression on #4, then either you have a blown head gasket or a damage engine.

    Reply to Comment

  • was pulling 2 codes bad coil and misfire. I replaced the coil now just a misfire. Shoul i replace the spark plug?

    Reply to Comment

  • You could try swapping the spark plug to see if the code follows the spark plug. If you haven't replace the plugs for a while, then you should do it anyways.

    Reply to Comment

  • I just bought the truck, going to replace all 8 coils and plugs. How long can i drive the truck with the flashing check engine light? Plugs should be here in a few days.

    Reply to Comment

  • It is difficult to say. It depends how far and how long you need to drive. The problem is that when there is no spark, unburned fuel goes to the Catalytic Converter and that may damage the cats.

    Reply to Comment

  • ok. The flashing only started today, The light has been on a few. I'm going to have to drive it a couple more days. Thanks for your quick response and help with this!

    Reply to Comment

  • could the bad coil have made the plug go bad? foul it up?

    Reply to Comment

  • Yes, definitely.

    Reply to Comment

  • cool! thanks! Spark plug should fix this! Thanks again!!!

    Reply to Comment