A mass airflow sensor is used to find out the mass of air entering a fuel-injected engine. The air mass information is necessary for the engine control unit (ECU) to balance and deliver the correct fuel mass to the engine. Air changes its density as it expands and contracts with temperature and pressure. If your mass air flow sensor is inoperative it can fail to deliver the proper amount of air or fuel into the intake, which has a tendency to dump more fuel then needed. You should have this problem taken care of.