A method and a system for detection of torque deviations of an engine (101) in a vehicle (100). A measurement (201) is made of actual measured values Dact related to a behavior of at least one parameter which is related to an actual torque Meng_act delivered by the engine (101). This actual torque Meng_act is delivered here by the engine (101) in consequence of a torque Meng_req demanded from the engine (101). A comparison (202) is then made of the actual measured values Dact which are related to the behavior of the at least one parameter with previously determined measured values Dref of correspondingly at least one respective parameter related to the actual torque Meng_act. The previously determined measured values Dref will here have been determined during normal operation of the vehicle (100). Detection is then made of whether the actual measured actual torque Meng_act deviates from the demanded torque Mengj-eq. The detection is based here on the comparison of the actual measured values Dact with the previously determined measured values Dref.