206 SW petrol engine turns off

I own a petrol 206 SW 2003 that has a curios malfuntion: when running normally, at any speed and under any circumstances, the engine sometimes simply turns off when i press the clutch to change gear. when the problem happens I hear a "tic tac" noise on the left side of the control panel and the rpm's goes up and down very fast (between 5000 and 15000 rpm's). Because of this malfuntionthe car has gone to the peugeot assistence shop at least 10 times. The lambda device has already been changed and the fuel injection system has been cleaned but the problem persists. ANY HELP WOULD BE APPRECIATED.