So let me get this straight .....you cant diagnose your engine problem BUT you are going to swap the whole engine out as if swapping the whole entire engine is easier than diagnosing the existing one in the car. I would go back to diagnosing before swapping engines, it seems we still don't know if it's a rod or a battery terminal problem. Swapping engines can potentially open a can of worms if the engines are of different years with different accessories and so on. BTW: is this a manual or automatic car??