BMW i8
Modular three-cylinder turbo with a lively character. Turbocharger and timing chain are wear items; vibration balance handled by a balancer shaft.
Three-Cylinder in a BMW
Three cylinders in a BMW — that feels wrong. Vibrates at idle and doesn't sound like Munich.
Engine Weaknesses 7
Same timing chain issue as N20 and B48. Plastic guide rails wear out, chain elongates. Slightly less loaded on the 3-cylinder.
Symptoms: Rattling on cold start, engine check light, rough idle
Early B38 engines (manual gearbox, built before April 2015) had an undersized crankshaft half-shell bearing. BMW switched to 360° bearings and replaced affected engines as a goodwill gesture (up to 120,000 km / 5 years).
Symptoms: Knocking or hammering from the engine block under load; oil pressure drop; in extreme cases engine seizure due to spun bearing
Turbocharger shaft seals become porous and allow oil into the combustion process. On the 3-cylinder, exhaust gas pressure pulses cause higher wear than on four-cylinders.
Symptoms: Blue smoke on cold start or wide-open throttle, oil consumption above 0.5 L/1,000 km, oil mist in intercooler, smoke after long motorway run.
Plastic cooling system components (expansion tank, hoses, flanges) develop hairline cracks and lose coolant gradually. On the 3-cylinder, thermal loads are higher due to uneven combustion.
Symptoms: Dropping coolant level without visible external leak, occasional coolant smell on exit, coolant warning light after longer drive.
As a direct-injection engine the B38 does not wash the intake valves with fuel. Blowby vapours and EGR recirculation promote coking. The three small-displacement cylinders are more sensitive than large four-cylinders.
Symptoms: Stumbling and misfires on cold start; power loss especially at low loads; uneven idle; increased fuel consumption
With frequent urban and short-trip driving the EGR valve gets clogged with soot deposits and sticks. Cleaning is often enough; in advanced cases the valve must be replaced.
Symptoms: Stumbling on cold start, increased fuel consumption, engine warning light (EGR fault), rough idle, occasional stalling in city traffic.
The 3-cylinder B38 produces more NVH than a four-cylinder due to its firing order. Engine mounts wear earlier from the uneven loading; steering column and steering wheel can vibrate.
Symptoms: Noticeable vibrations at idle, especially through steering wheel and gear knob; vibrations increase with failed engine mounts after 100,000 km
Vehicle Weaknesses 6
The carbon fibre reinforced polymer passenger cell (Life module) of the i8 cannot be repaired after accident damage — only replaced. BMW-approved specialist workshops are required. Minor damage often results in an insurance write-off.
A bursting coolant hose on the three-cylinder turbo causes overheating. Melted plastic enters the oil circuit and seizes the crankshaft bearings. Repair cost approximately €8,500.
As with many vehicles featuring a large high-voltage system, the i8's 12V auxiliary battery can fail prematurely. It powers all ancillaries and the HV control unit. Starting problems and system errors follow.
The i8's cross-drilled high-performance brake discs are susceptible to cracking. Regular inspection at every service is recommended.
The i8's temperamental fuel door fails to open reliably, especially with a near-empty tank. The emergency release behind the boot lining is often needed. Widely reported in forums as the most common minor fault.
A known weakness on older i8 models: the electric auxiliary heater (active only in pure EV mode) fails. Repair cost approximately €1,500.
Reports & Tests
9 owner complaints filed with NHTSA (2014–2020). Most reported: Electrical (4), Engine (3), Suspension (1).