Can I drive with P0304?

No, you should not drive with P0304. This code indicates a serious issue that requires immediate attention.

How much does it cost to fix P0304?

The typical repair cost for P0304 ranges from $20 to $800, depending on the root cause and whether you go to a dealership or independent shop.

Can I fix P0304 myself?

This repair is rated as "intermediate" difficulty. This repair requires some mechanical knowledge and basic tools.

The most common causes of P0304 include: Bad spark plug on cylinder 4, Faulty ignition coil for cylinder 4, Fuel injector 4 clogged or faulty. Check the diagnostic steps above for a systematic approach to identifying the root cause.

P0304 is rated as "serious" severity. This is a serious issue that should be fixed as soon as possible.

SAE Standard Definition

P0304

Cylinder 4 Misfire Detected

The engine is misfiring specifically in cylinder 4.

Serious Issue- Do not drive this vehicle

Serious

Do not drive intermediate Fix within 3 days

Estimated Cost (USD)$20 - $800

BudgetMajor

Estimated Labor~1 hours

The ECM has detected that cylinder 4 is contributing insufficient power relative to the other cylinders. A single-cylinder misfire typically points to a component specific to that cylinder: its spark plug, ignition coil, fuel injector, or a mechanical issue like low compression.

Symptoms

Check Engine Light on/flashing

Rough idle

Engine vibration

Loss of power

Fuel smell from exhaust

Common Causes

Bad spark plug on cylinder 4

HIGH

Worn, fouled, or damaged spark plug.

Faulty ignition coil for cylinder 4

HIGH

Coil-on-plug failure is common.

Fuel injector 4 clogged or faulty

MEDIUM

Injector not delivering proper fuel spray.

Low compression in cylinder 4

LOW

Blown head gasket, burned valve, or worn rings.

Step-by-Step Diagnosis

Replace spark plug 4

easy

Remove and inspect cylinder 4 spark plug. Replace if worn or fouled.

Tools:Spark plug socketTorque wrench

Swap ignition coil

easy

Swap cylinder 4 coil with an adjacent cylinder. If misfire moves, the coil is bad.

Tools:Socket set

Test fuel injector

medium

Listen to cylinder 4 injector with a stethoscope. It should click steadily. Check resistance (typically 12-16Ω).

Tools:StethoscopeMultimeter

Compression test

hard

Perform a compression test on cylinder 4. Should be within 10% of other cylinders.

Tools:Compression tester

Common Codes

P0300 Random Misfire: Causes, Diagnosis, and When to Worry

A random misfire code (P0300) can mean anything from worn spark plugs to a serious engine problem. Learn how to diagnose it and when it's actually dangerous.

Frequently Asked Questions

Summary

Category: Powertrain
System: Ignition System or Misfire
Cost Range: $20 - $800

Disclaimer

The information on this page is provided for general educational and reference purposes only. ErrorCodes is not a substitute for professional automotive diagnosis or repair. Diagnostic trouble codes indicate areas for further investigation and do not definitively identify the failed component. The same code can have different causes depending on your specific vehicle, its history, and conditions. Always consult a qualified, certified mechanic before performing repairs. ErrorCodes assumes no liability for any repairs made based on information found on this site.