P0306 on Porsche
Cylinder 6 Misfire Detected
P0306 on Porsche vehicles indicates cylinder 6 misfire detected. Au7o has documented this code across 3 Porsche models — most commonly on 911, Boxster, Cayman. This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. Typical repair costs on Porsche range from $6,000 to $25,000, depending on the specific model and root cause.
Common Causes of P0306
- •Worn or fouled spark plug on cylinder 6
- •Failed ignition coil for cylinder 6
- •Clogged, leaking, or failed fuel injector
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt valve, head gasket)
- •Damaged plug wire or coil connector
- •Carbon buildup or worn valvetrain components
P0306 on Porsche by Model
Porsche 911(1 issue)
- Cylinder Bore Scoring (Nikasil Wear)2009-2019
The 991-generation 911 suffers from cylinder bore scoring where the Lokasil cylinder liners develop deep vertical scores, typically on cylinders 1 and 6. This is caused by inadequate oil supply to the cylinder walls during cold starts and short-trip driving. The issue results in excessive oil consumption and eventually requires engine rebuild or replacement.
Porsche Boxster(1 issue)
- Cylinder Bore Scoring2005-2012
The M96 and M97 engines in the Boxster develop cylinder bore scoring similar to the 911. Scoring typically occurs on cylinders 1 and 6 due to uneven oil distribution in the flat-six layout. Symptoms begin with increased oil consumption and progress to misfires and rough running.
Porsche Cayman(1 issue)
- Cylinder Bore Scoring2006-2016
The Cayman M97 and MA1 flat-six engines develop bore scoring on cylinders 1 and 6, identical to the pattern seen in the 911 and Boxster. The Cayman GT4 with its 3.8L 911-derived engine is also affected. Oil starvation at the cylinder walls during cold starts is the primary cause.
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View P0306 across all makes →Frequently Asked Questions
What does P0306 mean on Porsche?▼
P0306 stands for "Cylinder 6 Misfire Detected." This code means the engine computer detected a misfire on cylinder 6 — that cylinder isn't burning its fuel-air mixture properly. The computer senses misfires by watching for tiny variations in crankshaft speed each time a cylinder should fire, and when cylinder 6 repeatedly fails to contribute, this code sets. You may feel a shake or stumble, especially at idle or under load, along with reduced power and possibly a flashing check-engine light, which signals a misfire severe enough to damage the catalytic converter. A misfire comes down to a problem with spark, fuel, or compression in that cylinder. On Porsche specifically, this code is documented across 3 models.
What causes P0306 on Porsche vehicles?▼
Common causes on Porsche: Worn or fouled spark plug on cylinder 6, Failed ignition coil for cylinder 6, Clogged, leaking, or failed fuel injector, Vacuum or intake air leak affecting that cylinder, Low compression (worn rings, burnt valve, head gasket). Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0306 on a Porsche?▼
Repair costs on Porsche range from $6,000 to $25,000, depending on the specific model and root cause.
Which Porsche models have P0306 documented?▼
Au7o has documented P0306 on 3 Porsche models: 911, Boxster, Cayman.