The invention discloses an online
diesel engine air valve state detection method. The method comprises the following steps: monitoring the instantaneous rotating speed, cylinder cover vibration, diesel consumption,
discharge temperature and
cooling water temperature of a
diesel engine through a sensor; converting signals collected in the first step into standard electric signals to be input in a
data acquisition card; carrying out acquisition and analog-to-
digital conversion on the standard electric signals by the
data acquisition card; by
coupling the
instantaneous speed of the diesel engineand the vibration of a cylinder, converting the vibration in a
time domain into an angle domain corresponding to a
crank angle for order analysis; measuring an order ratio
data matrix shown in the specification of the
diesel engine under
normal conditions; introducing the order ratio
data matrix in a formula to change the diesel consumption x g / kWh,
discharge temperature y K and
cooling water temperature z K into margin coefficients; and measuring an order ratio
data matrix B in arbitrary conditions, and comparing B with eta A, wherein, when B is greater than eta A, an air valve of the dieselengine is abnormal. According to the method, most faults of the air valve are judged in advance, so that a user is reminded of overhauling and replacing the air valve in advance.