This paper is on developing the advanced method in diagnosis electronic control of gasoline and LPG engine. The experimental methods using oscilloscope were employed to measure waveform of hot wire, hot film, oxygen, ignition coil and injector. Through these analysis, emission reduction and fuel economy improvement were expected by depict vehicles. The experiment was carried out during no-load condition. A summary of the important results are as follows. 1. The factors affecting the secondary ignition waveform from the primary ignition waveform were reverse surge voltage and induced voltage . Actually shape of primary ignition waveform was normal, but a secondary ignition waveform was measured badly. 2. The area of the voltage-time diagram of secondary ignition waveform means the value of the effective discharge of energy. This value is negative, the fuel economy could be predicted badly and is positive, good value of fuel economy could be predicted. 3. Inspection and maintenance of DLI ignition vehicles compared to DIS ignition vehicles were essential. The secondary ignition waveform of the C type vehicle were worst compare to those of the different type vehicles. The injection duration of injector was largest C, D types in the order named, was shortest E, F type. As a result, E, F type are most effective among Gasoline vehicles.