P0300
High SeverityRandom/Multiple Cylinder Misfire Detected
Ignition System
What Does P0300 Mean?
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.
Common Fix
Replace spark plugs
Estimated Cost (DIY)
$20 - $60
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
- 1Check spark plugs — replace if worn or fouled
- 2Inspect ignition coils for cracks
- 3Check for vacuum leaks
- 4Test fuel pressure
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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.