P0308: Cylinder 8 Misfire Detected
Updated November 12, 2026
Cylinder 8 isn't firing properly. The engine computer detects this as a small slowdown in crankshaft speed each time that cylinder should fire. It applies to V8 and larger engines.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- A worn or fouled spark plug in cylinder 8
- A failing ignition coil or plug wire for that cylinder
- A clogged or failing fuel injector, or a loose injector connector
- A vacuum leak near that cylinder, such as a leaking intake manifold gasket
- Low compression from a valve, ring or head gasket problem (less common)
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Rough idle or a shake at stops
- Hesitation or loss of power
- A flashing check engine light under load
- A fuel smell from the exhaust
Is it safe to drive?
A flashing check engine light means a severe misfire: stop driving as soon as it's safe and have the car towed, because unburned fuel can overheat and ruin the catalytic converter. With a steady light and a mild misfire, drive gently and get it fixed soon.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Confirm where cylinder 8 is on your engine; numbering varies by maker.
- With the engine off, swap the cylinder 8 coil (or plug wire) with a neighboring cylinder, clear the code and see whether the misfire follows the part.
- Pull and inspect the spark plug for wear, oil or carbon.
- If the ignition parts check out, inspect the injector connector and have the injector tested and a compression or leak-down test done.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
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Questions
What does P0308 mean?
P0308 is the generic OBD2 code for "Cylinder 8 Misfire Detected." Cylinder 8 isn't firing properly. The engine computer detects this as a small slowdown in crankshaft speed each time that cylinder should fire. It applies to V8 and larger engines.
Is it safe to drive with P0308?
A flashing check engine light means a severe misfire: stop driving as soon as it's safe and have the car towed, because unburned fuel can overheat and ruin the catalytic converter. With a steady light and a mild misfire, drive gently and get it fixed soon.
How do I check P0308 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Confirm where cylinder 8 is on your engine; numbering varies by maker. With the engine off, swap the cylinder 8 coil (or plug wire) with a neighboring cylinder, clear the code and see whether the misfire follows the part. Pull and inspect the spark plug for wear, oil or carbon. If the ignition parts check out, inspect the injector connector and have the injector tested and a compression or leak-down test done.
Related codes
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