My 2012 Chevy Impala was doing just fine until two weeks ago. I auto started my car, while walking up it shut off on its own. I got in the car and the check engine light came on as well messages for service Stabilitrack and Service Traction (something, I can quite remember). When I am at a complete stop the car stutters with vibration. I got the ignition coil in Cylinder 1 as well as the spark plugs for cylunders 1-6 changed. The car now switches gears at the proper time but there is still a stutter, When the spark plug is removed from cylinder 1 the car runs fine without the stutter. What could this be?