P0300 on Porsche
Random/Multiple Cylinder Misfire Detected
P0300 on Porsche vehicles indicates random/multiple cylinder misfire detected. Au7o has documented this code across 4 Porsche models — most commonly on 718 Cayman, 911, Boxster. P0300 means the engine computer detected misfires occurring randomly or across multiple cylinders rather than in one specific cylinder. A misfire is when a cylinder fails to ignite its fuel-air mixture properly, which the computer senses through small fluctuations in crankshaft speed. Because it's not isolated to one cylinder, the cause is usually something that affects the whole engine — like fuel, air, or ignition system problems — rather than a single coil or plug. Persistent or heavy misfiring wastes fuel, runs rough, and can damage the catalytic converter, which is why a flashing check engine light should be taken seriously. Typical repair costs on Porsche range from $700 to $25,000, depending on the specific model and root cause.
Common Causes of P0300
- •Worn or fouled spark plugs (across cylinders)
- •Vacuum or intake air leak
- •Weak fuel pump, clogged fuel filter, or low fuel pressure
- •Failing ignition coils or worn spark plug wires
- •Dirty or faulty mass airflow (MAF) sensor
- •Clogged or dirty fuel injectors
- •Faulty crankshaft/camshaft position sensor
- •Low compression or EGR/PCV system faults
P0300 on Porsche by Model
Porsche 718 Cayman(1 issue)
- Direct Injection Intake Valve Carbon Buildup2017-2025
The 718 Cayman turbo flat-four and naturally aspirated flat-six engines use direct injection, which does not wash the intake valves with fuel. Carbon deposits accumulate on the intake valves over time, restricting airflow and causing rough idle, misfires, and power loss. The turbo engines are more prone due to higher intake temperatures.
Porsche 911(3 issues)
- 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.
- Direct Injection Intake Valve Carbon Buildup2009-2019
The direct injection system on 991 engines does not spray fuel over the intake valves, allowing carbon deposits to accumulate on the valve stems and ports. Over time this restricts airflow, causing rough idle, misfires, and reduced power. The flat-six layout makes walnut blasting more labor-intensive than on inline engines.
- Timing Chain Tensioner and Guide Failure2009-2019
The 991-generation timing chain tensioners can lose hydraulic pressure, particularly after the car has been sitting for extended periods. This allows chain slack on startup, which can jump timing and cause catastrophic valve-to-piston contact. The plastic chain guides also wear prematurely on high-mileage engines.
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.
Looking for P0300 on a different make?
View P0300 across all makes →Frequently Asked Questions
What does P0300 mean on Porsche?▼
P0300 stands for "Random/Multiple Cylinder Misfire Detected." P0300 means the engine computer detected misfires occurring randomly or across multiple cylinders rather than in one specific cylinder. A misfire is when a cylinder fails to ignite its fuel-air mixture properly, which the computer senses through small fluctuations in crankshaft speed. Because it's not isolated to one cylinder, the cause is usually something that affects the whole engine — like fuel, air, or ignition system problems — rather than a single coil or plug. Persistent or heavy misfiring wastes fuel, runs rough, and can damage the catalytic converter, which is why a flashing check engine light should be taken seriously. On Porsche specifically, this code is documented across 4 models.
What causes P0300 on Porsche vehicles?▼
Common causes on Porsche: Worn or fouled spark plugs (across cylinders), Vacuum or intake air leak, Weak fuel pump, clogged fuel filter, or low fuel pressure, Failing ignition coils or worn spark plug wires, Dirty or faulty mass airflow (MAF) sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0300 on a Porsche?▼
Repair costs on Porsche range from $700 to $25,000, depending on the specific model and root cause.
Which Porsche models have P0300 documented?▼
Au7o has documented P0300 on 4 Porsche models: 718 Cayman, 911, Boxster, Cayman.