Engine-CodesCadillac – P0304 Cadillac

P0304 Cadillac Code - Cylinder 4 Misfire Detected

Quick Answer

When a Cadillac diagnostic code P0304 appears, it indicates that a misfire has been detected in cylinder 4 of the engine. Common causes include Worn or fouled spark plugs, Faulty ignition coil in cylinder 4, Clogged or faulty 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 Cadillac indicates Cylinder 4 Misfire Detected.
Common causes
Common causes include Worn or fouled spark plugs, Faulty ignition coil in cylinder 4, Clogged or faulty 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.
Table of contents Created and updated by William Orellana on Sep 07, 2024
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Code P0304 Cadillac Description

When a Cadillac diagnostic code P0304 appears, it indicates that a misfire has been detected in cylinder 4 of the engine. A misfire occurs when the fuel-air mixture in the cylinder fails to ignite properly, causing the engine to run rough and potentially impacting performance. Cylinder 4 is one of the cylinders in the engine's combustion chamber, and a misfire in this cylinder can lead to a variety of issues.

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

Common Causes of P0304 Cadillac

  1. Worn or fouled spark plugs.
  2. Faulty ignition coil in cylinder 4.
  3. Clogged or faulty fuel injector.
  4. Vacuum leak in the intake manifold.
  5. Low compression in cylinder 4.

Symptoms of P0304 Cadillac

  1. Rough idling or shaking while the engine is running.
  2. Lack of power or acceleration when driving.
  3. Engine misfires or hesitation during acceleration.
  4. Increased fuel consumption.
  5. Illumination of the check engine light on the dashboard.

How to Fix P0304 Cadillac

  1. Begin by scanning the vehicle's computer for any additional diagnostic trouble codes and to confirm the cylinder 4 misfire.
  2. Inspect and potentially replace the spark plugs in cylinder 4.
  3. Check the ignition coil for cylinder 4 and replace if necessary.
  4. Test the fuel injector in cylinder 4 for proper function.
  5. Conduct a compression test on cylinder 4 to verify engine health.

Cost to Fix P0304 Cadillac

The cost of repairing a cylinder 4 misfire on a Cadillac can vary depending on the specific cause of the issue and the parts and labor required. On average, the cost can range from $100 to $500 for parts and labor. It's important to note that diagnostic time and labor rates at auto repair shops can vary, so it's recommended to obtain quotes from multiple sources before proceeding with the repair.

Tech Notes for P0304 Cadillac

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".

There is a Factory Service Bulletins for All 2000-2020 Cadillac Models:
2000-2020 Cadillac Factory Service Bulletin OBDII Code P0304
This Factory Service Bulletin explains how this condition may be caused by significant carbon build-up on the intake and/or exhaust valves due to fuel contamination or incomplete burning of the fuel.

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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 Cadillac Code

1. What does the OBDII code P0304 mean on a Cadillac?

P0304 indicates that the engine control module (ECM) has detected a misfire in cylinder 4 of your Cadillac.

2. What are the common symptoms of a P0304 code in a Cadillac?

Symptoms can include rough idling, reduced engine performance, poor fuel economy, hesitation during acceleration, and the check engine light turning on.

3. What causes a P0304 code on a Cadillac?

Common causes include a faulty spark plug, ignition coil, fuel injector issues, vacuum leaks, low compression in cylinder 4, or a problem with the ECM.

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

Driving with a P0304 code can cause further engine damage, including damage to the catalytic converter, so it’s best to address the issue promptly.

5. How do I diagnose a P0304 code on a Cadillac?

Start by inspecting the spark plug, ignition coil, and fuel injector for cylinder 4. You may also need to perform a compression test or check for vacuum leaks.

6. How much does it cost to fix a P0304 code on a Cadillac?

The cost varies depending on the cause, ranging from $50 for a spark plug replacement to several hundred dollars for more complex repairs like fixing low compression.

7. Can a dirty fuel injector trigger a P0304 code?

Yes, a clogged or dirty fuel injector can cause insufficient fuel delivery to cylinder 4, leading to a misfire and triggering the P0304 code.

8. Will replacing the spark plug for cylinder 4 fix the P0304 code?

If the spark plug is the root cause of the issue, replacing it may resolve the problem. However, other components should also be inspected to rule out additional causes.

9. Could a vacuum leak cause a P0304 code in a Cadillac?

Yes, a vacuum leak near cylinder 4 can disrupt the air-fuel mixture, resulting in a misfire and triggering the code.

10. How can I prevent a P0304 code from occurring again?

Regular maintenance, including timely replacement of spark plugs, ignition coils, and fuel filters, as well as using high-quality fuel, can help prevent a recurrence of the P0304 code.

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