My gas mileage drop I already change the fuel pump, coils and cleaned the Oxygen sensors but I still get low gas mileage on my car
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1999 Toyota Corolla Question: Gas mileage
Answer #1patrick mannion from Greg Solow's Engine Room, August 31, 2009, 20:59Master
There is no real way to clean the Air fuel ratio/O2 sensor the sensor is key to fuel efficiency but the pattern has to be monitored on an oscilloscope to determine if it is OK or not. Your car has On Board Diagnosis 2 (OBD2) using a scan tool it would be interesting to see what the Long Term and Short Term Fuel Trim figures are , a scan tool can show if the computer is adding or subtracting fuel. The air flow meter and coolant temperature sensor are two other key inputs contributing to good fuel economy.
Here is a US government link to Corolla MPG.