I don't think punting on 4th and 14 was the right call for the Rams. It reminds me of when Andy Reid went for it on 4th and 25 in week one.
First, you have the players to convert it. It's not like you're a one-dimensional offense and rely exclusively on the run. Stafford, Puka, and Kupp were carving us up at times, and had already converted at least one 3rd and 15 earlier in the game.
Second, the relative benefit isn't there. They punted from the 44 and DPJ went out of bounds at the 17. So they gained 27 yards of field position. With about 4 minutes left and the Rams having only one timeout and the two-minute warning, no matter where the Lions got the ball, the name of the game was getting 2-3 first downs. Getting it at the 44 might marginally increase the odds we kick a long field goal to go up 4, but that would take at least one first down anyway. In other words, you're probably losing anyway. Whether your defense makes a stand at the 44 or the 17, it wouldn't matter. They'd need to do it. Give your offense one more shot.
The calculus is a little different if Ford Field doesn't force two timeouts. At that point, you can be selective in using those and make the Lions stretch the field more.