A tune up isn't what it used to be; a seasonal oil change and carburetor adjustment. What is involved in a modern tune up is the replacement of the spark plugs, spark plug wires, fuel filter, air filter and performing a fuel system service (cleaning the fuel injectors, intake and the Mass Air Flow sensor). All of these components need to be working properly to maintain the correct air to fuel ratio. The Mass Air Flow sensor is one of many very important sensors, which help the computer decide how much fuel should be administered to the engine. A dirty sensor can't accurately read the amount of air entering the engine and will, therefore, transmit incorrect information to the computer.
