The Subaru Ascent has carved a niche in the three-row SUV segment, offering a blend of capability, comfort, and technology that appeals to families and adventure seekers. At the heart of this vehicle lies the turbocharged 2.4-liter FB24 engine, a powerplant designed to deliver a spirited driving experience while maintaining daily usability. However, like any complex mechanical device, this engine is not immune to specific issues that owners and potential buyers should be aware of.
Understanding the FB24 Powerplant
The FB24 represents Subaru's modern approach to forced induction, pairing a compact turbocharger with direct injection to produce 260 horsepower and 300 lb-ft of torque. This unit was introduced to replace the legacy naturally aspirated units, aiming to provide a more refined yet powerful driving dynamics. The design emphasizes a lighter rotating assembly and a sophisticated cooling system to manage the thermal loads inherent in turbocharged operation.
Common Mechanical Concerns
While many owners experience trouble-free ownership, certain mechanical issues have been reported with notable frequency. These problems often stem from the intricate nature of turbocharged engines and the specific materials used in their construction. Addressing these early can prevent more significant damage and costly repairs down the line.
Valve Stem Seal Degradation
One of the most frequently cited issues involves the degradation of the valve stem seals. These components are responsible for preventing oil from entering the combustion chamber. When they fail, the engine exhibits blueish exhaust smoke, particularly during cold startup or after periods of inactivity. This phenomenon, known as "burning oil," not only creates a visible emission issue but also leads to a gradual loss of oil pressure if left unchecked.
Turbocharger System Vulnerabilities
The turbocharger, while enhancing performance, introduces additional points of potential failure. Owners have reported issues related to the wastegate actuator and the associated vacuum lines. A failing wastegate can cause the engine to lose power, create a whining noise, or result in excessively high boost pressure. Furthermore, the intercooler piping connections have been noted as potential leak points, which can manifest as a hissing sound and a drop in overall efficiency.
Electrical and Sensor Complications
Modern engines rely heavily on a network of sensors to optimize performance and emissions. The Ascent's FB24 is no exception, and some owners have encountered problems with specific components that can trigger the check engine light and disrupt the engine's operation.
Mass Air Flow Sensor (MAF) Issues
The MAF sensor measures the volume of air entering the engine, a critical data point for the ECU to calculate the correct fuel mixture. When these sensors fail or become coated with debris, the engine may run lean or rich, leading to hesitation, stalling, or reduced fuel economy. Cleaning or replacing the sensor typically resolves these symptoms.
Ignition Coil Failures
Ignition coils are responsible for converting the battery's voltage into the high voltage needed to spark the plugs. Subaru coils have been known to degrade over time, particularly due to the heat cycles they endure. A failing coil will cause a misfire, which feels like a sudden loss of power or a rough idle, and can damage the catalytic converter if the issue persists.
Preventative Maintenance Strategies
Proactive care is the most effective way to mitigate the risks associated with the Ascent's engine. Adhering to the manufacturer's recommended service schedule is the first line of defense. However, given the specific issues highlighted, owners may consider additional vigilance in certain areas.
Monitor oil levels frequently, ideally monthly, and top off with the manufacturer-specified synthetic oil.
Be attentive to any changes in exhaust smoke, especially during cold mornings.
Address any check engine lights promptly with a diagnostic scan to identify the specific fault code.
