Imputed righteousness is the very person of Christ living on the inside of a believer, not an abstract concept which covers our past, present or future sin, or "good works" for that matter.
it sounds like you are mixing up imputed righteousness with infused righteousness. Imputed righteousness is the righteousness credited to our account when we believe the Gospel. It is a righteousness not our own but imputed to us on account of Christ.
When we become a Christian (accept Christ into your heart), we have Christ's righteousness imputed (charged) to us, like an electrical invigoration of imputation. We are then like Him. I hope this makes sense. This 'righteousness', or, right standing with God does not automatically elect us into heaven, it is by this grace thought that we CAN have salvation.
I just did a thread on this concept but, yes, it's very well said by crossfyre, crossnoted, with only adding that because of the blood of Christ, though we still do sin, it is covered by the blood of Christ and that covering, from our having CONFESSED, and, confessing now, and, in the future, as we are LED by Him in us, makes us 'not sin,' as Scripture states clearly, 'Born of God, one does not sin.' 1 John 3: 6 and 3:9 say the say thing, might be the only place in Scripture, too, where the same words are repeated within so short a timeframe of each other, 'course, the words are slightly different, 'whoever abides in Him does not sin,' is verse 6 and verse 9 is more like what crossfyre speaks of in our having Christ in us, 'Whoever has been born of God does not sin...' and, to continue,
"...for His seed remains in him and he cannot sin, because he has been born of God (born again, born of water and of spirit, God's Holy Spirit in Him).
James 2:23 "And the Scripture was fulfilled which says, "Abraham believed God, and, it was accounted to Him for righteousness. And he was called a friend of God."