A probe and method for sensing pressure variations in the exhaust stream of an engine for detecting cylinder misfires. The probe includes a Venturi tube placed in the exhaust stream. The Venturi tube has a sensing tube with an aperture, and the sensing tube is coupled to a pressure sensor for monitoring the pressure of the exhaust stream within the Venturi tube at the point of the aperture. The pressure sensor then generates a voltage signal based on the pressure, and this voltage signal is viewed on an oscilloscope or processed by a microprocessor to generate a waveform readable by a technician. The waveform will indicate the presence of a misfiring cylinder(s), and more specifically, which cylinder(s) is misfiring.