By the real meaning of the engine P1121 Code, it becomes easier to solve the problem from the car engine. This problem has started after the spot serious harm. You need to change the engine or fix it. Else, if it is just a stuff of grime buildup or soft plugs, only clean these components. If your chains are twisted, avoid arcing and harm instigated by resistance by using a incentive plug wire loom or partition on your car. Principally it arranges your cables and proposal better insulation. Do not allow any wrong meaning or anyone to solve the car engine problem.