P0300

High Severity

Random/Multiple Cylinder Misfire Detected

Ignition System

P0300 — Instant Answer

Random/Multiple Cylinder Misfire Detected

Severity: HIGH SEVERITY

Meaning: The engine is misfiring across multiple cylinders. This is often caused by something that affects all cylinders — spark plugs, fuel quality, vacuum leak, or low compression.

Safe to drive? NO if CEL is flashing. YES with caution if solid, but repair this week.

Estimated repair cost: $20 - $500

Most common causes:

  • 1. Worn spark plugs (35-45% of cases)
  • 2. Bad ignition coils (10-25% of cases)
  • 3. Vacuum leak affecting multiple cylinders (10-25% of cases)
  • 4. Low fuel pressure (10-25% of cases)

Symptoms

  • ⚠️Rough idle
  • ⚠️Flashing check engine light
  • ⚠️Loss of power
  • ⚠️Engine shaking or vibration

Common Causes

Worn spark plugslikely
Bad ignition coilspossible
Vacuum leak affecting multiple cylinderspossible
Low fuel pressurepossible

How to Diagnose P0300

  1. 1Check spark plugs — replace if worn or fouled
  2. 2Inspect ignition coils for cracks
  3. 3Check for vacuum leaks
  4. 4Test fuel pressure

OEM Procedures for P0300

Random/Multiple Cylinder Misfire Detected Found 34 OEM service manual procedures.

Ignition Coil

Ignition Coil

Ignition Coil
No link

Ignition Coil & ICM Replacement (HVS) - Installation

Ignition Coil
No link

Ignition Coil & ICM Replacement (HVS) - Installation

Ignition Coil
No link

Ignition Coil & ICM Replacement (HVS) - Installation

Ignition Coil
No link

Ignition Coil & ICM Replacement (HVS) - Installation

Ignition Coil
No link

Ignition Coil & ICM Replacement (HVS) - Installation

Ignition Coil
No link

Ignition Coil & ICM Replacement (HVS) - Installation

Ignition Coil
No link

Ignition Coil & ICM Replacement (HVS) - Installation

Ignition Coil
No link

Showing 8 of 34 procedures

OEM Diagnostic Flowchart

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Parts & Tools for This Job

Common parts shoppers buy for P0300 Random/Multiple Cylinder Misfire Detected.

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Priority exact repair pages for this code family

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Related Resources

Repair guides, symptom pages, and wiring diagrams related to P0300.

Frequently Asked Questions

Is P0300 serious?
Yes — a flashing check engine light means active misfires that can damage the catalytic converter. Pull over if the light flashes.
Can bad gas cause P0300?
Yes — contaminated or low-octane fuel can cause random misfires. Try running a tank of premium fuel with fuel system cleaner.

Find your service manual

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Author & Review

Published by AllOEMManuals, founded by Lyndon Bedford, an automotive technician with 20 years of experience. He owned and operated a mechanic shop in Hurst, Texas from 2014 to 2022 and continues hands-on repair work.

Content may combine manual references, general repair templates, and AI-assisted drafting. Confirm the source, vehicle configuration, and applicability before working. Report corrections through our contact page.

Last updated: 2026-11-13

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