My check engine light came on. I got a bunch of codes, two of which specifically pinpointed an oxygen sensor. But after I replaced the O2 sensor I had P0171 & P0174 codes coming up together. At Autozone the default answer anything related to this is "buy new O2 sensors, mass air flow sensors, etc". You could easily spend hundreds of dollars on this stuff. It wound up being a vacuum leak at the rear of the intake manifold. A $9 gasket on the Air Valve Assembly. To find the leak spray carb cleaner all around your intake manifold and connecting lines. If you engine reves up or begins to stall out, its a vacuum leak. If you get codes p0171 and p0174 together, DO NOT go crazy replacing O2 sensors and the like. Check for vacuum leaks first! This little fix has improved my gas mileage and helped my engine run much better!
My check engine light came on. I got a bunch of codes, two of which specifically pinpointed an oxygen sensor. But after I replaced the O2 sensor I had P0171 & P0174 codes coming up together. At Autozone the default answer anything related to this is "buy new O2 sensors, mass air flow sensors, etc". You could easily spend hundreds of dollars on this stuff. It wound up being a vacuum leak at the rear of the intake manifold. A $9 gasket on the Air Valve Assembly. To find the leak spray carb cleaner all around your intake manifold and connecting lines. If you engine reves up or begins to stall out, its a vacuum leak. If you get codes p0171 and p0174 together, DO NOT go crazy replacing O2 sensors and the like. Check for vacuum leaks first! This little fix has improved my gas mileage and helped my engine run much better!
- Miguel T., Tucson, AZ, US