Before you cut off all the connectors to butt splice, apply some DeoxIT. If you have the spray version, just undo the connectors and spray into both male and female pins. Then connect and disconnect the Molex connector several times. In addition to deoxidizing, it also provides some lubrication to the pins.
https://www.amazon.com/dp/B00006LVEU...n_title_1&th=1
There is also a high potency version. It just takes a drop. But there is no carrier solvent to insure dispersal and coverage like with the spray can version. Thus, it's limited to applications where you have easy access to the contacting material of the connector.
https://www.amazon.com/dp/B0000YH6F8...d_asin_title_2
Ron