P0300: Random/Multiple Cylinder Misfire Detected
Your engine is misfiring on multiple cylinders randomly. This means the combustion process is failing in more than one cylinder, which can cause rough running, poor performance, and potential engine damage if ignored.
Symptoms
- Rough idle or shaking
- Check engine light (flashing = severe misfire)
- Hesitation under acceleration
- Poor fuel economy
- Possible fuel smell from exhaust
Causes (Ranked by Likelihood)
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DIY Fix Steps
⚠ Safety first: work on a cold engine, chock wheels, use jack stands - never rely on a floor jack alone.
Use an OBD2 scanner with live data to see which cylinders are misfiring. If random, suspect ignition system or fuel.
Check plug condition. Carbon fouling = rich mixture. White/gray = lean. Gap at manufacturer spec (usually 0.030"-0.044").
If misfiring coil swaps to a different cylinder when you move it, the coil is bad. Replace the failing coil.
With engine running, spray carb cleaner around intake manifold gaskets and vacuum lines. RPM change = leak found.
After repairs, clear DTCs and drive 50+ miles. If code returns, proceed to fuel pressure testing.