rattles really bad when push on gas no power to go uphill what could be wrong on 1990 Cadillac DeVille

it happens all the time and it's a little shaky not sure if its the muffler or something else but it does not have any power to go up hill add it sounds like I'm going to break something when I push on the gas

Asked by for the 1990 Cadillac DeVille
poss timing issues. have a diag done to be sure