Porsche Turbo
The MA1.71 is the first 991 Turbo: 3.8L biturbo on the new 9A1 crankcase, no Mezger lineage anymore. The move away from the GT1 block solves the coolant pipe adhesive problem — but brings new quirks. The engine is more compact, more rev-happy and thermally more balanced than its predecessor. VTG turbochargers remain a Porsche exclusive: no turbo lag, linear power delivery from just under 2,000 rpm. Direct injection still means valve coking over time. The early 991.1s had a weakness on the right turbo-to-intercooler hose, which Porsche fixed with a revised part number. HPFP failure and bore scoring are rare, but should be ruled out via borescope and oil analysis when buying used.
991 Turbo — The Competence Package
383 kW, AWD, PDK — the 991 Turbo is not a feeling, it is a fact. The biturbo boxer delivers torque in every situation, PDK shifts faster than any human, AWD distributes the power precisely. Sonically sober, dynamically brutally competent. Not the most emotional 911, but one of the most capable.
Engine Weaknesses 8
DFI high-pressure fuel pump on the left cam drive fails internally. Fuel pressure drops, engine management switches to limp mode. Replacement parts are hard to source.
Symptoms: Extended cranking, engine briefly runs then dies, 'Engine power reduced', fault code P1023
The 9A1 engine with Alusil coating shows bore scoring less often than the M97 but remains susceptible — particularly at cold starts below -10 °C and with dirty injectors.
Symptoms: Rhythmic knocking (engine noise), increased oil consumption, misfires, sooty right exhaust side, aluminium particles in oil filter
PDK distance sensor puts the gearbox into limp mode. Porsche's standard fix is a full gearbox swap — specialists repair just the sensor for significantly less.
Symptoms: Fault codes P1731–P1734, no reverse gear, gearbox limp mode, 'Transmission fault' display
VTG actuator linkage rusts through moisture and salt ingress. Ball joints seize, turbo runs without geometry control. Less common than on the 997 generation.
Symptoms: Inconsistent boost build-up, overboost or absent boost, actuator no longer audible when ignition is on
The right turbo-to-intercooler hose on early 991.1 cars seals inadequately — oil from the crankcase leaks out and drips to the ground. Porsche revised the part number.
Symptoms: Oil spots under right side of car, visible oil film on hose, faint oil smell when engine is warm
Typical DFI valve carbonisation. Intake valves are never washed by fuel — crankcase blow-by oil bakes on. Cleaning is time-consuming as engine removal is necessary.
Symptoms: Light hesitation at part throttle, marginally higher consumption, measurably reduced power with heavy build-up
991-generation ignition coils differ from the 997.2 series. Heat and salt ingress cause cracks. Replace all six when one fails.
Symptoms: Misfires, engine stumble under load, check engine light, rough idle
Eight solenoids in the vacuum system control exhaust flaps, heater valves and other actuators. Early 991.1 models were covered by service campaign WC-43. Revised part number is more durable.
Symptoms: Coolant fault, climate control failure, exhaust flap issues, cooling system warning, check engine light
Vehicle Weaknesses 7
HVAC blend door actuators fail and cause incorrect air temperatures. Recoding required after replacement.
Brake pads and brake discs wear significantly faster than expected under sporty use. PCCB ceramic brakes are less affected.
Door and window seals harden over time. Water enters the interior in heavy rain.
On cars driven in winter, exhaust nuts, bolts and underbody fasteners seize solid with road salt. Follow-on costs arise from snapped studs during the next service.
Door cards, rear parcel shelves and B-pillar trims creak and rattle over road imperfections. Cause: plastic clips and metal contact points without adequate damping.
Active engine mounts with Sport Chrono package lose their damping control due to internal sensor failure. Often just the sensor needs replacing, not the complete mount. Primarily affects 991.1 from around 30,000 km.
Both AC condensers sit exposed behind the front bumper and are frequently damaged by stone impacts. Refrigerant escapes slowly or suddenly. Replacing both condensers plus the dryer at the same time is recommended.