P0300 on MINI
Random/Multiple Cylinder Misfire Detected
P0300 on MINI vehicles indicates random/multiple cylinder misfire detected. Au7o has documented this code across 6 MINI models — most commonly on Cooper, Cooper S, Coupe. 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 MINI range from $200 to $3,000, 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 MINI by Model
MINI Cooper(1 issue)
- N12/N16 Timing Chain Tensioner Failure2007-2013
The R56 Cooper's N12 and N16 engines suffer from premature timing chain tensioner and guide rail failure. The plastic chain guides deteriorate, causing chain slack that leads to rough running, rattling on startup, and potential catastrophic engine damage if the chain jumps timing.
MINI Cooper S(2 issues)
- N14/N18 Turbo Engine Timing Chain Catastrophic Failure2007-2013
The R56 Cooper S N14 engine (2007-2010) is particularly notorious for timing chain tensioner failure, even more so than the naturally aspirated N12. The higher cylinder pressures from turbocharging accelerate chain stretch and guide rail wear. The revised N18 (2011-2013) improved but didn't fully resolve the issue.
- Direct Injection Carbon Buildup on Intake Valves2007-2025
All turbocharged direct-injection MINI engines (N14, N18, B46/B48) accumulate carbon deposits on intake valves since fuel is injected directly into the cylinder rather than washing over the valves. This reduces airflow and causes rough running.
MINI Coupe(1 issue)
- N14/N18 Timing Chain Tensioner Failure and Chain Stretch2012-2015
The MINI Coupe uses the N14 (early JCW) or N18 (Cooper S) turbocharged engines which are prone to timing chain stretch and tensioner failure. The plastic chain guide rails wear prematurely, and the hydraulic tensioner loses its ability to keep the chain taut. A stretched chain causes rough idle, misfires, and eventually can jump teeth, causing catastrophic valve-to-piston contact. The N14 is more prone than the N18 but both are affected.
MINI GP(3 issues)
- Carbon Buildup on Intake Valves (Direct Injection) Causing Misfires/Power Loss2013-2021
Direct-injection turbo engines in MINI GP models can accumulate carbon deposits on intake valves because fuel does not wash the valve backs. Over time this can cause rough idle, hesitation, misfires, and reduced performance, especially noticeable on cold starts. This is widely documented in MINI owner reports and service bulletins covering DI drivability complaints on N18/B48 platforms.
- Oil Separator / Crankcase Ventilation Valve Failure Causing Oil Consumption (N14/N18)2007-2014
The N14 and N18 engines fitted to the GP1 and GP2 are well-documented for crankcase ventilation oil separator (CCV) failure, where the plastic separator housing cracks or the internal membrane fails. A failed CCV causes excessive oil to be drawn into the intake manifold and combustion chambers, resulting in visible blue smoke from the exhaust and abnormally high oil consumption between service intervals. MINI issued TSB SI B11 06 11 addressing this concern on N14 and N18 engines.
- Turbocharger Oil Feed Line Leak and Carbon Buildup2013-2021
The GP's high-output turbocharged engine is pushed harder than standard Cooper S models, making it more susceptible to turbo oil feed line leaks and carbon buildup on intake valves. The banjo bolt oil feed line seal hardens over time, causing oil to drip onto the exhaust manifold. Direct injection also causes severe intake valve carbon deposits that reduce performance.
MINI Hardtop 4 Door(1 issue)
- B38/B48 Engine Timing Chain Stretch and Rattle2015-2019
The MINI Hardtop 4 Door uses BMW-developed B38 (3-cylinder) and B48 (4-cylinder) engines that can develop timing chain stretch, particularly on early production units. The chain stretches beyond the tensioner's compensation range, causing a rattle on cold start and eventually triggering cam position correlation faults. The B38 3-cylinder is more susceptible due to the higher vibration levels of a 3-cylinder engine. BMW/MINI has issued technical updates for the chain and tensioner.
MINI John Cooper Works(1 issue)
- Intake Valve Carbon Buildup from Direct Injection2008-2024
All MINI JCW models with direct injection (both N14 and B48 engines) accumulate carbon deposits on the intake valves because fuel is injected directly into the cylinder rather than washing over the valves as in port injection engines. Over 30,000-50,000 miles, carbon buildup restricts airflow, causing rough idle, misfires, reduced power, and poor fuel economy. The N14 engine (2008-2012) is particularly susceptible due to its higher oil consumption contributing additional oil vapor to the intake tract.
Looking for P0300 on a different make?
View P0300 across all makes →Frequently Asked Questions
What does P0300 mean on MINI?▼
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 MINI specifically, this code is documented across 6 models.
What causes P0300 on MINI vehicles?▼
Common causes on MINI: 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 MINI?▼
Repair costs on MINI range from $200 to $3,000, depending on the specific model and root cause.
Which MINI models have P0300 documented?▼
Au7o has documented P0300 on 6 MINI models: Cooper, Cooper S, Coupe, GP, Hardtop 4 Door, John Cooper Works.