RPM running to high and don't kick down on 2005 trailblazer

My 2005 trailblazer automatic ! had a almost new engine put in April. Ran perfect. It started pour oil and my rpm would not kick down without me letting off gas. Both started at the same time ! Oil issue ended up being a bad oil sending sensor. But now RPM are still high. I can give it light steady gas and it will kick down and go till about 3 rpm. then it shoots way over 6 till i let off gas. I can slowly give gas again and it goes but rpm never goes under 3 or 4 while giving gas. Other than that it runs fine. I have no engine light so computer don’t read anything ! I’m lost. It’s like driving a standard and not properly shifting