A unique technique is proposed based on restricted Boltzmann machine (RBM) and softmax regression for automated fault detection and classification using the acoustic signal generated from IC (Internal Combustion) engines. This technique uses RBM for unsupervised fault feature extraction from the frequency spectrum of the noisy acoustic signal. These extracted features are then used to reduce the dimensionality of the training and testing data vectors. These reduced dimensionality data vectors are used by softmax regression-based classifier for classification of the engine into faulty and healthy class. The proposed technique does not require any hand-engineered feature extraction, as usually done. This technique performs very well with a small number of training data. The overall performance of this technique for four different fault classes is more than 99\% on the industrial IC engine data. In a typical case, with only 38 training data sets and 210 test data sets, the performance is 99.52\%.