The crew executed an approach in manual mode with the co-pilot flying the airplane. The airplane landed normally on runway 29L at Tehran-Mehrabad. After compression of the main struts of the landing gear, the spoilers were extended. At the same time the reverser on the left engine was brought to maximum mode. The reverse thrust lever of the right engine was not used since the reverser was deactivated. After deceleration to a speed of 80 knots the reverse thrust lever of the left engine was brought to the intermediate position between maximum and minimum reverse thrust. As this was happening the throttle control lever of the right engine was brought from idle to the position of ~55 degrees according to FDR data. Further movement of the reverse thrust lever of the right engine was accompanied by the simultaneous shifting of the throttle control lever of the left engine practically as far as the nominal mode. At this moment the airplane captain interfered in the control, shifted the throttle control lever of the right engine to idle and again activated maximum reverse of the left engine. However, in spite of the actions taken, the airplane overshot the runway at a speed of about 40 knots.