Acura MDX doesn't accelerate more than gear two or 3. I also noticed that the D5 keeps blinking after driving and going to park. Just today, the A/T light just came up. What's happening?
Sounds like it's in limp home mode. You really (!!) need to get the code(s) read to get an idea what's going on with your transmission. There are a LOT of things that can cause the symptoms you're seeing - some are relatively trivial to fix, and some point at a toasted transmission.
Along those lines - how many miles on the vehicle, and has the transmission fluid ever been changed?