Forester Power Loss Points to Major Engine Problems

Having dealt with a similar issue on my 2020 Outback, I understand your concern about the engine performance problems. These symptoms often point to potential ECU issues, especially if there has been any aftermarket modifications. After noticing similar power loss and dashboard light warnings, I discovered it was related to a faulty chip tuning job done by a third-party shop. The vehicle diagnostics revealed multiple fault codes pointing to ECU communication errors. The auto scanner showed similar symptoms to what you are describing, reduced power output and engine performance issues. The fix required a complete reset of the ECU and removal of the problematic tuning software, costing 180€ at an authorized dealer. The car has been running perfectly since then. To better assist with your specific case, could you share: Has the vehicle had any recent modifications or tuning work? What specific fault codes did your scan tool show? When did you first notice the power reduction? Are there any other warning lights besides the check engine light? This information would help determine if your issue stems from similar causes or if there might be other underlying problems requiring attention.

Thanks for sharing the diagnostic codes. I just had my 42468 KM service done last month, and the fault codes showing up on my car computer were P0172 and P0174. Using my auto scanner revealed these diagnostic codes point to a rich fuel mixture condition. After investigating further, a faulty mass airflow sensor was causing incorrect readings, leading to poor engine performance. The car showed the exact same symptoms, sluggish acceleration and reduced power output. Before taking it to a shop, try disconnecting the battery for 15 minutes. This can sometimes reset the system and temporarily resolve fault codes if they were triggered by a one-time event. If the issue persists, professional diagnosis would be the next step since multiple systems could be involved. Let us know what the readings show if you run another scan tool check. The exact diagnostic codes can help pinpoint whether this is a sensor issue or something more serious.

Thanks for the follow-up about the P0172 and P0174 codes. My Outback actually showed those exact same diagnostic codes when I was dealing with the rich fuel mixture problem. The car computer was definitely picking up incorrect readings from the mass airflow sensor, just like in your case. I tried the battery disconnect reset you mentioned, but in my situation, the dashboard light came back on within a day. The scan tool kept showing the same fault codes even after multiple resets. When I finally took it to have a proper car diagnostic done, they confirmed the mass airflow sensor was the culprit, but also found some carbon buildup was contributing to the problem. The total repair ended up costing 320€, which included cleaning the intake system and replacing the faulty sensor. The engine power returned to normal immediately after the fix, and the diagnostic codes haven't reappeared in the 6 months since. One thing I learned from this, while the fault codes pointed to a rich mixture condition, having professional diagnostic testing done helped identify the complete problem rather than just treating the symptoms. The carbon buildup might have caused more issues if left unchecked.

I really appreciate all the detailed feedback. After connecting the dots between my symptoms and your similar experiences with fault codes P0172 and P0174, I decided to have the vehicle properly diagnosed. The car diagnostic confirmed our suspicions about the mass airflow sensor being the primary issue. The engine issue turned out to be exactly what we discussed, a faulty sensor combined with some carbon deposits. The auto scanner readings were spot-on, and the mechanic showed me how the car computer was receiving incorrect data from the compromised sensor. The total repair came to 295€, which covered both the sensor replacement and a thorough intake cleaning. The dashboard light disappeared immediately after the fix, and the engine performance returned to normal. The sluggish acceleration is completely gone. For anyone searching the forums later with similar symptoms, having the proper car diagnostic done early saved me from potential additional damage. While the battery reset trick can help identify temporary issues, persistent fault codes like these usually indicate a genuine problem requiring professional attention.