A faulty mass air flow (MAF) sensor can cause erratic/rough engine operation and fuel economy issues. Since this sensor measures the actual amount of air entering the motor, when it fails, the engine control module (ECM) takes the wrong information and delivers incorrect volumes of fuel to the cylinders.
Erratic Engine Operation and Poor Fuel Economy Due to Faulty Mass Air Flow Sensor on Mercedes-Benz S320
Average mileage: 180,800 (175,000–186,600)
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I have replaced plugs, wires, and plugs and I'm still having poor fuel economy and my rpm guage goes up and down and sometimes cuts off. When I'm driving, theres a bad rough vibration in the car. Replaced air filter and oil change. I cleaned the EGR valve and still runs rough.