Engine Shaking? P0301 Cylinder 1 Misfire – Causes, Fixes & Repair Cost

The P0301 trouble code means the engine has detected a misfire specifically in Cylinder 1.

A misfire happens when fuel inside the cylinder does not burn correctly, causing vibration and power loss.

Modern ECUs detect misfires by monitoring crankshaft speed changes.

Typical Symptoms

• Engine shaking at idle

• Power loss

• Rough acceleration

• Check Engine Light flashing

• Increased fuel consumption

If the light is flashing — repair immediately.

Most Common Causes

🔧 Bad Spark Plug (MOST COMMON)

Worn or fouled spark plugs cause incomplete combustion.

⚡ Faulty Ignition Coil

Cylinder-specific misfires are often ignition coil related.

⛽ Fuel Injector Issue

Injector clogging may reduce fuel delivery.

🌬 Vacuum Leak Near Cylinder 1

Unmetered air causes unstable combustion.

How Mechanics Diagnose P0301

• Swap ignition coil with another cylinder

• Inspect spark plug condition

• Check injector pulse

• Perform compression test

If misfire moves → ignition problem confirmed.

Repair Cost

Is P0301 Serious?

Yes — prolonged misfires can destroy the catalytic converter.