Ask Andy AIP0306 Cylinder 6 Misfire Detected
What it means, what causes it, and what it costs to fix.
What P0306 means
The engine computer watches crankshaft speed. When cylinder 6 doesn't push the crank as hard as the others, the fuel in that cylinder isn't burning properly. Because the code names one cylinder, the cause is usually a part that serves only that cylinder: its spark plug, ignition coil, or fuel injector.
Can I drive with P0306?
Severity: High. Fix right away. It can cause damage or leave you stranded.
Drive gently and only short distances. If the check engine light is flashing, stop. A steady misfire dumps unburned fuel into the exhaust and can overheat and destroy the catalytic converter.
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Ask Andy about P0306Symptoms
- Rough or shaky idle
- Hesitation or stumble when accelerating
- Check engine light, possibly flashing
- Loss of power and worse fuel economy
- Raw-fuel smell from the exhaust
Common causes
Most likely first.
- Worn or fouled spark plug in cylinder 6
- Failing ignition coil (coil-on-plug) on cylinder 6
- Clogged or leaking fuel injector for cylinder 6
- Vacuum leak near that cylinder's intake runner
- Low compression: burnt valve, worn rings, or a head gasket leak
How to diagnose P0306
- Pull all codes. A lean code (P0171/P0174) alongside it points toward a vacuum leak or fuel delivery problem.
- Swap cylinder 6's ignition coil with a neighboring cylinder, clear the code, and drive. If the misfire moves to the other cylinder, the coil is bad.
- Pull the spark plug and check the gap, wear, and fouling (oil, fuel, or white deposits).
- Listen to the injector with a stethoscope, or swap it, to confirm it is clicking and spraying.
- If plug, coil, and injector check out, run a compression or leak-down test on that cylinder.
Tip: most US auto parts stores will read your codes for free.
Repair costs
| Spark plug | $20–$60 DIY, $100–$250 at a shop |
| Ignition coil | $40–$150 part, $100–$300 installed |
| Fuel injector | $150–$500 installed |
| Valve or head gasket repair (low compression) | $1,000–$3,000+ |
Typical US prices. Your vehicle, region, and shop rates will change these.
P0306 FAQ
What does P0306 mean?
P0306 means "Cylinder 6 Misfire Detected." The engine computer watches crankshaft speed. When cylinder 6 doesn't push the crank as hard as the others, the fuel in that cylinder isn't burning properly. Because the code names one cylinder, the cause is usually a part that serves only that cylinder: its spark plug, ignition coil, or fuel injector.
Can I drive with a P0306 code?
Drive gently and only short distances. If the check engine light is flashing, stop. A steady misfire dumps unburned fuel into the exhaust and can overheat and destroy the catalytic converter.
What is the most common cause of P0306?
The most common cause is: Worn or fouled spark plug in cylinder 6. Other causes include failing ignition coil (coil-on-plug) on cylinder 6 and clogged or leaking fuel injector for cylinder 6.
How much does it cost to fix P0306?
Typical repairs run about $20 to $3,000 in the US, depending on the cause. Spark plug: $20–$60 DIY, $100–$250 at a shop.
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