Can I keep driving with a P0301 code?

Only as little as you must, and gently. If the light is flashing, stop and shut off the engine. An active misfire pushes raw fuel into the exhaust, which overheats the catalytic converter and can destroy it. Even with a steady light, the engine can hesitate or stall, so avoid hard acceleration, towing, and highway trips until it is fixed.

Is P0301 just a bad spark plug, or something worse?

Often it is just the plug, which is the cheapest and most likely fix. Next most common is the ignition coil, then the fuel injector. If those check out and the misfire stays, it can be a mechanical problem like a burned valve or worn rings, which costs far more. Test before you assume the worst.

I replaced the spark plugs and coils and still have P0301. What now?

Stop buying ignition parts. A single-cylinder misfire that survives a new plug and coil usually means a fuel or mechanical fault. Check the injector on cylinder 1 first. If that is fine, get a compression or leak-down test, because a burned valve, worn rings, or a head gasket leak will not be fixed by more coils.

Codes › P0301

P0301: Cylinder 1 is misfiring and not burning fuel right

Cylinder 1 Misfire Detected

High severityCan you keep driving?

Drive as little as possible, and only gently. If the check engine light is flashing, stop and shut the engine off. A flashing light means an active misfire is dumping raw fuel into the exhaust and cooking your catalytic converter.

What it means

Your engine fires each cylinder in turn to make power. P0301 means cylinder 1 keeps failing to burn its fuel right. The computer catches this by watching for tiny drops in crankshaft speed when that cylinder should be pushing. Unlike P0300, which is a random misfire, P0301 points at one specific cylinder. That makes it easier to solve, because something about cylinder 1's spark, fuel, or compression is failing. The most common causes are cheap and simple, so do not panic and buy expensive parts before you test.

Common causes

Worn or fouled spark plugThe most likely cause and the cheapest fix. Plugs wear out on a schedule, so start here.
Failed ignition coil on cylinder 1Common on higher-mileage engines with a coil on each plug. The classic single-cylinder misfire part.
Clogged or faulty fuel injector on cylinder 1Less common than ignition parts. The usual next suspect when the misfire does not follow the coil or plug.
Vacuum or intake gasket leak near cylinder 1A leak at one runner leans out that cylinder. Cheap to find with a smoke test or spray.
Low compression from a burned valve, worn rings, or head gasketLess frequent but the priciest outcome. The answer when plugs, coils, and injector do not fix it.
Sensor, wiring, or timing fault, or just low fuelRare and usually comes with other codes. A near-empty tank can set this on some cars.

What it costs

Spark plug replacement$60 to $400
Ignition coil replacement$150 to $550
Fuel injector replacement$250 to $950
Vacuum or intake gasket repair$100 to $400
Compression repair (valves, rings, head gasket)$1,000 to $3,500
Catalytic converter, if the misfire damaged it$1,000 to $2,500

Symptoms

Check engine light on, and flashing if the misfire is severe
Rough or shaky idle and engine vibration
Hesitation, stumbling, or jerking under acceleration and loss of power
Hard starting or occasional stalling
Worse fuel economy, higher emissions, sometimes a fuel smell from the exhaust
In mild cases, no symptoms besides the light

What to do next

Do not throw a full set of coils and plugs at it. Carmakers' own service bulletins prescribe a free test: swap cylinder 1's ignition coil with a neighbor, clear the code, and see if the fault follows. If the misfire moves to that cylinder (P0301 becomes P0302), the coil is bad. Do the same with the plug to isolate a bad plug. If P0301 stays after a new plug and coil, stop buying ignition parts. The next step is a compression or leak-down test, because a stubborn single-cylinder misfire with good spark and fuel is a mechanical problem. Also check the simple things, like a near-empty tank or a damaged injector connector.

Lewis reads P0301 and any partner misfire codes, plus the live misfire counts and fuel trim data, so you can see which cylinder is dropping and how hard. Download Lewis.

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FAQ

Can I keep driving with a P0301 code?: Only as little as you must, and gently. If the light is flashing, stop and shut off the engine. An active misfire pushes raw fuel into the exhaust, which overheats the catalytic converter and can destroy it. Even with a steady light, the engine can hesitate or stall, so avoid hard acceleration, towing, and highway trips until it is fixed.
Is P0301 just a bad spark plug, or something worse?: Often it is just the plug, which is the cheapest and most likely fix. Next most common is the ignition coil, then the fuel injector. If those check out and the misfire stays, it can be a mechanical problem like a burned valve or worn rings, which costs far more. Test before you assume the worst.
I replaced the spark plugs and coils and still have P0301. What now?: Stop buying ignition parts. A single-cylinder misfire that survives a new plug and coil usually means a fuel or mechanical fault. Check the injector on cylinder 1 first. If that is fine, get a compression or leak-down test, because a burned valve, worn rings, or a head gasket leak will not be fixed by more coils.