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Engine-Codes – Mercury – P0304 Mercury

P0304 Mercury Code - Cylinder 4 Misfire Detected

Quick Answer

When the diagnostic trouble code P0304 appears on a Mercury vehicle, it indicates that there is a misfire detected in cylinder 4 of the engine. Common causes include Faulty spark plug in cylinder 4, Malfunctioning ignition coil specific to cylinder 4, Clogged fuel injector supplying cylinder 4. 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 Mercury indicates Cylinder 4 Misfire Detected.
Common causes
Common causes include Faulty spark plug in cylinder 4, Malfunctioning ignition coil specific to cylinder 4, Clogged fuel injector supplying cylinder 4.
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 12, 2024
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Code P0304 Mercury Description

When the diagnostic trouble code P0304 appears on a Mercury vehicle, it indicates that there is a misfire detected in cylinder 4 of the engine. A misfire occurs when the fuel-air mixture in the cylinder fails to ignite properly, leading to a disruption in the engine's combustion process. This can result in a loss of power, rough idling, decreased fuel efficiency, and potential damage to the catalytic converter over time.

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

Common Causes of P0304 Mercury

  1. Faulty spark plug in cylinder 4.
  2. Malfunctioning ignition coil specific to cylinder 4.
  3. Clogged fuel injector supplying cylinder 4.
  4. Vacuum leak affecting cylinder 4.
  5. Low compression in cylinder 4 due to issues such as a worn piston ring or valve.

Symptoms of P0304 Mercury

  1. Rough idling or shaking sensations while the engine is running.
  2. Decreased acceleration and power when driving.
  3. Increased fuel consumption and reduced fuel efficiency.
  4. Illumination of the check engine light on the dashboard.
  5. Potential engine stalling or hesitation while driving.

How to Fix P0304 Mercury

  1. Begin by connecting an OBD-II scanner to the vehicle to confirm the presence of code P0304 and identify the specific cylinder affected.
  2. Inspect the spark plug in cylinder 4 and replace it if necessary. Also, check the ignition coil for any signs of damage or malfunction and replace if needed.
  3. Clean or replace the fuel injector supplying cylinder 4 to ensure proper fuel delivery.
  4. Check for any vacuum leaks in the system, focusing on hoses and connections near cylinder 4.
  5. Perform a compression test on cylinder 4 to determine if there are any issues with piston rings or valves causing low compression.

Cost to Fix P0304 Mercury

The cost of repairing a misfire in cylinder 4 of a Mercury vehicle can vary depending on the specific cause of the issue and the parts needed for repair. On average, the cost of parts such as spark plugs, ignition coils, fuel injectors, and compression testing tools can range from $100 to $500. Labor costs at an auto repair shop typically range from $80 to $150 per hour, with the total repair bill potentially amounting to $300 to $800 or more. It is advisable to consult with a certified mechanic or service center to obtain a more accurate estimate based on the vehicle's make and model, as well as the extent of the repairs required.

What does this mean?

Tech Notes for P0304 Mercury

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.











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Information for Specific Mercury 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 Mercury Code

1. What are the common symptoms of OBDII code P0304 in a Mercury, indicating Cylinder 4 Misfire Detected?

The common symptoms include rough idling, loss of power, engine hesitation, and potentially increased fuel consumption.

2. What are some possible causes of OBDII code P0304 in a Mercury?

Common causes of this code could include a faulty ignition coil, spark plug, fuel injector, vacuum leak, or low compression in the affected cylinder.

3. How can I diagnose the source of the misfire in Cylinder 4 of my Mercury triggering code P0304?

To pinpoint the issue, you can perform tests such as checking the spark plug, ignition coil, fuel injector, compression test, and inspecting for vacuum leaks.

4. What are some tips for repairing OBDII code P0304 related to Cylinder 4 Misfire in a Mercury?

Consider replacing the spark plug, ignition coil, or fuel injector in Cylinder 4, addressing any vacuum leaks, and performing a compression test to identify and fix the misfire.

5. Can a dirty or clogged fuel injector cause OBDII code P0304 in a Mercury?

Yes, a dirty or clogged fuel injector supplying insufficient fuel to Cylinder 4 can lead to misfires and trigger code P0304 in a Mercury.

6. Will driving with OBDII code P0304 in a Mercury cause further damage to the engine?

Continuing to drive with code P0304 may potentially cause damage to the catalytic converter due to unburned fuel entering the exhaust system.

7. Is it safe to reset the OBDII code P0304 in a Mercury after experiencing Cylinder 4 misfire?

While resetting the code may temporarily turn off the check engine light, it is recommended to diagnose and fix the underlying issue causing the misfire to prevent further problems.

8. Can a bad ignition coil be the sole reason for OBDII code P0304 in a Mercury?

Yes, a faulty ignition coil in Cylinder 4 can cause a misfire and trigger code P0304 in a Mercury.

9. How important is it to address OBDII code P0304 promptly in a Mercury?

It is crucial to address code P0304 promptly to prevent potential engine damage, maintain optimal fuel efficiency, and ensure smooth engine operation.

10. Are there any preventive maintenance steps to avoid OBDII code P0304 in a Mercury?

Regularly servicing and inspecting the ignition system, fuel system, and engine components can help prevent misfires and the occurrence of code P0304 in a Mercury.

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