My engine (2009 Auris TR 1.6 Valvematic, 43000 miles) has just been diagnosed, again, with a misfire. This is an old problem on this car which over the past year or so has regularly and frequently come up with an engine warning light which I extinguish by disconnecting / reconnecting the Battery. The car  has been into a main dealer on two separate occasions but after several hours investigation the  cause of the problem has not been identified.The fault code is P0302. I would welcome any sugges