P0300 Code: Random/Multiple Cylinder Misfire Detected

🟠 Moderate severity · drivable

If the check engine light is flashing, stop driving immediately — that means a severe misfire is dumping raw fuel into the converter. A steady light is usually safe for a short drive to a shop.

What P0300 means

The engine computer has detected misfires on multiple cylinders at random, rather than on one specific cylinder. A misfire means a cylinder isn't firing properly, which wastes fuel and can damage the catalytic converter.

Symptoms

Check engine light on (flashing if severe)
Rough idle or shaking engine
Loss of power or hesitation
Poor fuel economy
Strong fuel smell from the exhaust

Common causes

most common: Worn or fouled spark plugs
common: Failing ignition coils or plug wires
common: Vacuum leak
less common: Clogged fuel injectors or low fuel pressure
less common: Low compression from worn engine internals

How to fix it

Fix	DIY?	Typical cost
Replace worn spark plugs	Yes	$40–200
Replace failing ignition coils or plug wires	Yes	$50–400
Find and repair vacuum leaks	Yes	$10–100
Run a compression test to rule out internal engine wear	Mechanic	$100–200

Frequently asked questions

Is it safe to drive with a P0300 code?

Only if the light is steady and the car runs acceptably. A flashing check engine light means a severe misfire — stop and get it towed to avoid damaging the catalytic converter.

What causes a random misfire?

The most common causes are worn spark plugs, bad ignition coils, and vacuum leaks. A random pattern (versus one specific cylinder) often points to a shared issue like fuel or air delivery.

How much does it cost to fix a P0300?

Most fixes run $40–$400. Spark plugs are cheap; ignition coils and deeper fuel-system repairs cost more.