This report describes the principle and experimental investigation of a technique for detecting air-leakage in an internal combustion engine intake manifold. Air-leakage in intake manifold always affects the volumetric efficiency and fuel consumption of internal combustion engine and degrades the overall engine performance. It is well known to be detrimental that the engine system stability and performance must be taken into account in regular maintenance. Conventional method of air-leakage detection in intake manifold is hearing acoustic emission by an experienced technician when the engine in operation condition. Obviously, the conventional technique is not a precision approach for air-leakage detection. In the present study, a continuous wavelet transform technique using acoustic emission is applied to detect the air-leakage in an internal combustion engine intake manifold system. Experiments are carried out to evaluate the acoustic emission using proposed technique under various engine operation conditions. The results indicate that the proposed technique is effective in air-leakage detection of engine intake manifold system.