Alfa 156 MAF Sensor Issues Causing Engine Problems

Had almost the same issue with my 2003 Alfa 155 Diesel last winter. With some experience working on cars, I can say these symptoms are classic signs of a defective mass air flow sensor. The check engine light and poor fuel economy were the first signs. The air-fuel ratio was completely off, causing the engine to run rich and produce smoke. After checking the air filter and finding it clean, the workshop confirmed the MAF sensor was the culprit through diagnostic testing. The repair cost me 365 Euro including parts and labor. Since the fix, fuel consumption returned to normal and the engine runs smoothly again. The smoke issue disappeared completely. To better assist with your specific case, could you share: Current mileage on your 156, When was the last time the air filter was changed, Any diagnostic codes you might have pulled, Whether symptoms get worse during cold or hot weather These old Alfa engines are quite sensitive to air intake issues, but once fixed properly, they run like new again.

Last service was done at 94345 KM and included a full diagnostic check. The air filter and fuel filter were also replaced then. The air-fuel ratio issues have definitely gotten worse since that service. The engine stalling is most noticeable during cold starts, and the poor fuel economy is really hitting my wallet now. The MAF sensor readings are erratic according to my OBD scanner. Running the car in warmer weather seems to improve performance slightly, but the excessive fuel consumption and smoke are still present. The engine stalling happens regardless of temperature though. Would replacing the MAF sensor fix all these symptoms, or should I be looking at other potential causes of the air intake problems?

Thanks for those details on your 156. After fixing my 155 MAF sensor, I learned quite a bit about the air intake system on these engines. The erratic MAF sensor readings from your OBD scanner strongly support what I experienced. The cold start issues and temperature-related performance changes are also very similar to what I dealt with. When the mass air flow sensor fails, it cant properly measure the air-fuel ratio, leading to those exact symptoms. In my case, replacing just the MAF sensor fixed: The excessive fuel consumption, Cold start stalling, Smoke during acceleration, Check engine light, Performance decline in all weather conditions One word of caution from my experience, check the wiring connection to the MAF sensor before replacement. My mechanic found some corrosion on the connector pins, which we cleaned as part of the fix. The fact that your air filter is relatively new rules out one common cause of similar symptoms. This further points to the MAF sensor being the primary issue, just as it was in my case. A new MAF sensor should resolve all these problems, based on how identical the symptoms are to what I experienced with my Alfa.

Thanks for the helpful information about the MAF sensor issues. It looks like my symptoms match exactly what you experienced with your car. The matching symptoms really help confirm my suspicions about the faulty sensor. The check engine light, stalling, and high fuel consumption are getting worse by the day. Since my air filter is new and the OBD readings show erratic MAF sensor data, I feel confident moving forward with the replacement. I will definitely have the wiring connections checked for corrosion before installing the new sensor. Getting the air-fuel ratio back to normal should solve the smoke issues and improve the overall performance. I will schedule the repair next week and make sure they inspect the entire air intake system while replacing the MAF sensor. Hopefully this will get my fuel economy back to normal and eliminate the cold start problems. Thanks again for sharing your experience. It really helped confirm the diagnosis and gave me a clear path forward for fixing these issues.