P0300: Random/Multiple Cylinder Misfire Detected

The engine module detects misfire from crankshaft speed: a cylinder that does not fire gives no acceleration impulse. At a catalyst-damaging rate (CARB: at least 5 % per 200 revolutions) the warning light flashes; at an emissions-relevant rate (at least 1 % per 1,000 revolutions – GM about 2–5 %, Ford 0.9–1.5 %) it comes on after two trips. Ford and GM may shut off a misfiring cylinder's injector to protect the catalyst. P0300 sets when the misfire cannot be assigned to one cylinder: several cylinders each account for more than 10 %, the cylinder changes randomly, or – at Ford – the cylinder cannot be identified at high speed. It often appears together with cylinder codes. Causes are usually systemic: false air, worn plugs on several cylinders, fuel pressure or fuel quality, valve timing – and false detection from a damaged tone wheel, rough roads or vibration. Bulletins name coils, cracked plug insulators and wrong plug gaps.

Symptoms

• Check engine light on, flashing at a catalyst-damaging rate
• Rough idle, jerking, vibration
• Loss of power, hesitation
• Smell of unburnt fuel, higher consumption

Most likely causes

• False air (vacuum leak, crankcase ventilation, intake gasket)
• Worn or wrong spark plugs on several cylinders, faulty ignition coils
• Fuel pressure too low or high, contaminated fuel
• Valve timing (stretched chain), valves, compression on several cylinders
• False detection: tone wheel or pulley, rough road, vibration, software

What to check, in order

Start with the simplest. You can tick off each step.

1. See whether the light is flashing: if so, reduce engine load and avoid driving
2. Inspect the spark plugs, coils, and connectors
3. Swap the coil with another cylinder and see if the misfire moves with it
4. Check the injector and look for air leaks
5. Run a compression test if everything above checks out

Good to know

• Repair difficulty: medium
• It can trigger limp mode.
• It affects emissions.

What each character of P0300 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 3: Ignition and misfires
• 00: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0300?

If the check engine light flashes or the engine shakes hard, stop as soon as possible and do not keep driving. If the light is steady and the engine is only slightly rough, drive gently and only to the nearest repair shop.

What causes code P0300?

The most common causes are: false air (vacuum leak, crankcase ventilation, intake gasket); worn or wrong spark plugs on several cylinders, faulty ignition coils; fuel pressure too low or high, contaminated fuel.

Related codes

• P0301Cylinder 1 Misfire Detected
• P0302Cylinder 2 Misfire Detected
• P0316Engine Misfire Detected on Startup (First 1000 Revolutions)
• P0315Crankshaft Position System Variation Not Learned
• P0171System Too Lean Bank 1
• P0420Catalyst System Efficiency Below Threshold Bank 1

Sources

• law.cornell.edu: 13 CCR 1968.2
• gsi.ext.gm.com: 18OBDG03A Engine Diagnostics
• newtonnet.co.uk: fordobd2012
• saabwisonline.com: p0300 00

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.