Subaru Legacy MAF Sensor Issues Causing Engine Trouble

Having medium experience with car repairs, I dealt with a very similar issue on my 2006 Subaru Impreza last year. The symptoms matched exactly what you describe, poor fuel economy, rough idling, and performance decline during acceleration. After some initial attempts to clean the air intake system myself, I took it to a workshop where they diagnosed a faulty MAF sensor. The air-fuel ratio was completely off, causing the engine management system to feed either too much or too little fuel. The repair cost me 365€ including diagnostics, parts, and labor. Since the fix, the engine runs smooth again and fuel consumption returned to normal levels. To provide more specific advice for your case, could you share: any error codes from the check engine light? When was the last time you changed the air filter? Does the problem get worse when the engine is warm or cold? Have you noticed any unusual sounds from the engine bay? These details would help determine if your Legacy has the same root cause as my Impreza had.

Last maintenance was at 181042km and I also noticed similar issues with stalling and poor performance. My mechanic discovered the mass air flow sensor was indeed malfunctioning, affecting the air-fuel ratio significantly. After cleaning it thoroughly, the check engine light persisted. Running diagnostics revealed the sensor needed replacement. The complete repair included: New MAF sensor, Air filter replacement, Intake system cleaning Total cost was 420€ and the fuel economy improved immediately. The engine now runs smoothly without stalling. Would recommend getting diagnostic codes read first before replacing parts.

Thanks for the update on your Legacy repair. Your experience matches what I encountered with my Impreza perfectly. The MAF sensor failure tends to cause these exact symptoms, and replacing both the sensor and air filter as a package is the right approach. After my repair, I also noticed the fuel economy stayed consistently better. The initial investment of 365€ actually paid off through reduced fuel consumption. Important to note that simply cleaning the MAF sensor sometimes only provides temporary relief, which is why replacement was the better long-term solution in both our cases. For anyone else reading with similar symptoms, watching for these early warning signs can prevent more serious engine issues: Sudden drops in fuel economy, Engine stalling at idle, Rough acceleration performance, Check engine light activation Regular air filter maintenance can help prevent premature MAF sensor failure. Since the repair, I check my air filter every 15000km as preventive maintenance.

Thanks for confirming my suspicions about the MAF sensor. Getting the diagnostic codes was definitely the right first step before jumping into repairs. The 420€ total seems reasonable considering the complete service package. Since the repair, my fuel economy has returned to normal levels, dropping from 12L/100km back to around 9L/100km. The engine stalling issues have completely disappeared, and acceleration feels smooth again without any smoke. The air-fuel ratio is now properly regulated, which has made a huge difference in overall performance. For others with similar symptoms, here are the actual error codes I got: P0101 (Mass Air Flow Circuit Range/Performance), P0171 (System Too Lean) Looking back, the gradual decline in fuel economy should have been my first warning sign of sensor failure. At least now I know to watch for these symptoms and get them checked early. Will definitely keep up with regular air filter maintenance to prevent future MAF sensor issues.