Most people think that when their car does not run properly in some way that it must need a tune up. It could be idling rough, it could be hard to start, it could lack power, it could be getting poor mileage or have many other possible symptoms. While a tune up solves many of the problems above, there can be other underlying factors that cause the vehicle to behave in certain ways that a tune up will not fix. Besides, modern cars do not require tune ups and poor performance almost always means the car needs a repair.
The expression “Tune Up” is from a time when automobiles were not computer controlled and an auto mechanic could actually adjust the timing, idle speed, fuel mixture and other things to “Tune Up” the operation of the Engine, very much the same way a guitar player tunes up his/her instrument to bring it to proper pitch and operation by adjusting the tension on the strings. A present-day tune up involves replacing and servicing the wear items in the ignition and fuel systems by replacing air and fuel filters as well as spark plug electrodes.
After a tune up is performed, there will be a need to do some cleaning or decarbonizing of the throttle body and fuel system from the oil vapors produced by the positive crankcase ventilation (PCV) System. In general there are no adjustments needed (or possible) for the most part, because the engine computer controls all the functions of the Ignition and Fuel System.