THE NEW HOTNESS

Good day to all. I recently came across a deal on a w211 equipped with the m273(e55) engine . The previous owner just finished completing a engine swap, and stated that he couldn't get rid of a miss fire . He was pretty forward about everything and the car came with a bunch of extra parts that backup his claims so I bought it . The car was running bad and had no power so getting it onto trailer took a couple attempts . When I got it home I checked the coil packs on all cylinders and they were all good except for one ( checked the old fashion way plugged them out while listening for a difference) . While doing that I also got to see wich cylinders were not getting power from the engine harness and in doing that I learned that power was only being supplied to the same 3 cylinders , and I learned this by moving every coil pack around . So I'm assuming that I would have to purchase a whole new engine harness to fix this issue, I'm going to check all the fuses/relays today that could contribute to this since this is my first benz just to be sure and also learn but I have a gut feeling that would be the fix and have me able to see what that 400hp/tq can do . Any help or knowledge would be well appreciated . Boring my friend scanner to pull codes