Calibra 2.0l only over three cylinders

Hello guys! I have a problem… I bought a Cali and didn’t really look at the engine:-( now the evil came to wake… The engine runs very unevenly and I have already changed everything that can only be changed….but it still runs unround…Then I thought I would pull the line when the engine runs off the cords…Did then pull off the first three and it was all as it should be,but then the last one and then it was the Mototrlie f unchanged, whether with the cord or without the…. Now my question to you what can that be???? Is the 1st cylinder up your ass or can it be anything else????? Please help me have never had such a thing…… Then I say thanks for your help… Mfg Markus