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Engine Misfire: Rough Running and Combustion Failure

One or more cylinders failing to fire on each combustion cycle

What It Is

An engine misfire occurs when a cylinder fails to complete a normal combustion event. This can be due to insufficient spark (ignition misfire), insufficient fuel (lean misfire), or insufficient compression (mechanical misfire). The result is an uneven, sputtering, or stumbling engine note, often accompanied by a check engine light and misfire-specific OBD-II codes.

How Our AI Detects It

Symptoms

• Rough, uneven idle with a stumbling or loping quality
• Hesitation or surging during acceleration
• Check engine light, often flashing during an active misfire
• Noticeably reduced power and fuel economy
• Smell of unburned fuel from the exhaust
• Engine vibration felt through the steering wheel, pedals, or seat

Ford F-150 5.4L V8 with known spark plug ejection issues; Chevrolet Silverado 5.3L with AFM-related lifter and valve issues; Toyota Camry 2GR-FE V6 with age-related coil failure.

Estimated repair cost: $80–$300 for spark plug and coil replacement; $400–$1,200 for injector service; $2,000–$5,000 for mechanical causes such as head gasket

What Happens If Ignored

Not Safe to Drive

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Also Searched For

Sputtering Coughing

Frequently Asked Questions

Why does my check engine light flash instead of staying on?

A flashing check engine light specifically indicates an active misfire severe enough to damage the catalytic converter. Pull over and address the issue before continuing to drive.

Can a bad oxygen sensor cause misfires?

A faulty O2 sensor can cause the ECU to miscalculate fuel trim, leading to a lean or rich condition that causes misfires. However, most O2 sensor issues cause stumbling rather than confirmed cylinder-specific misfires.

How do I know if it is an ignition or fuel misfire?

Swap the coil from the misfiring cylinder with an adjacent one and rescan with an OBD-II reader. If the misfire code moves to the new cylinder, the coil is bad. If it stays, the injector or compression is the issue.

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