My 93 lumina 3.1L when getting warm will die, cough and sputter intermittingly. Engine lights flashing, rad fans kick in and out, ac clutch clicking (even when not being used). But all i have to do is turn key to off and it will start right back up depending on how hot it is. Changed lots of sensors including temp. sensor. Would it be safe to say ecm is the problem and if i get one to match does it have to be flashed? Any ideas much appreciated,thanks!!