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P0304 2003 Infiniti G35 Code - Number 4 Cylinder Misfire Detected

Quick Answer

When a misfire occurs, engine speed will fluctuate. Common causes include Faulty Spark Plug #4, Clogged or faulty Fuel Injector #4, Faulty Ignition Coil #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 2003 Infiniti G35 indicates Number 4 Cylinder Misfire Detected.
Common causes
Common causes include Faulty Spark Plug #4, Clogged or faulty Fuel Injector #4, Faulty Ignition Coil #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.
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Table of contents Created and updated by William Orellana on Mar 29, 2024
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Code P0304 2003 Infiniti G35 Description

When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor signal to vary, the Engine Control Module (ECM) can determine that a misfire is occurring. The Diagnostic Trouble Code (DTC) will be set when the Engine Control Module monitors the crankshaft speed and has detected that engine cylinder #4 is misfiring.
OBDII Code P0304 2003 Infiniti G35 - Number 4 Cylinder Misfire Detected - AutoCodes.com
P0304 2003 Infiniti G35 Code - Number 4 Cylinder Misfire Detected
What does this mean?

What are the Possible Causes of the DTC P0304 2003 Infiniti G35?

  • Faulty Spark Plug #4
  • Clogged or faulty Fuel Injector #4
  • Faulty Ignition Coil #4
  • Fuel Injector #4 harness is open or shorted
  • Fuel Injector #4 circuit poor electrical connection
  • Ignition Coil #4 harness is open or shorted
  • Ignition Coil #4 circuit poor electrical connection
  • Insufficient cylinder 4 compression
  • Incorrect fuel pressure
  • Intake air leak

How to Fix the DTC P0304 2003 Infiniti G35?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0304 2003 Infiniti G35 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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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 2003 Infiniti G35 Code

1. What does OBDII code P0304 mean for a 2003 Infiniti G35?

P0304 indicates a misfire in cylinder number 4, meaning the engine isn’t firing properly in that specific cylinder.

2. What are the common symptoms of code P0304?

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

3. What causes a P0304 code in a 2003 Infiniti G35?

Common causes include a faulty spark plug, bad ignition coil, clogged fuel injector, vacuum leak, low compression, or issues with the wiring or connectors.

4. Can a dirty or clogged fuel injector cause a P0304 code?

Yes, a clogged or malfunctioning fuel injector can disrupt the fuel delivery to cylinder 4, causing a misfire.

5. How do you diagnose a P0304 code?

Start by inspecting the spark plug, ignition coil, and fuel injector for cylinder 4. Check for vacuum leaks, test cylinder compression, and examine the wiring and connectors for damage.

6. Can a vacuum leak trigger a P0304 code?

Yes, a vacuum leak near cylinder 4 can cause an incorrect air-fuel mixture, leading to a misfire and triggering the code.

7. How serious is the P0304 code on a 2003 Infiniti G35?

While the vehicle may still run, ignoring the issue can cause further engine damage, reduced performance, and higher repair costs.

8. What’s the first step to fix a P0304 code?

Begin by replacing the spark plug in cylinder 4, as it’s often the simplest and most common cause of a misfire.

9. Can a faulty ignition coil cause a P0304 code?

Yes, a failing ignition coil for cylinder 4 can prevent proper spark delivery, resulting in a misfire.

10. Is it safe to continue driving with a P0304 code?

It’s not advisable. Driving with a misfire can damage the catalytic converter, worsen engine performance, and lead to more costly repairs.

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