I am having trouble fingering this passage. It is fast, quarter note = 140 or so. I was thinking:
3432 -- 3454 -- 3423 -- 1213
the start is fine but as it descends the 1213 stumbles me. Any suggestions?
This is all somewhat subjective, but I'd either pick 1313 or 1212 for the last group. Both prevent somewhat awkward shifting, as also mentioned by Scott. The 12 feels slightly less natural due to the close position of the thumb to the index finger (e.g., a trill would normally be done 1-3 instead of 1-2), but may work out well in this case.
Contrary to the suggestions above the first four notes in the next bar, I would actually play 1313 there, putting the longer middle finger on the black keys and keeping the thumb on the f. It doesn't matter whether the next pattern goes up or down after that: the crossing of the 3 over the 1 is quite natural. I agree with alephzero that the 1 on the e-flat is not obvious, as it shifts the hand needlessly forward onto the keyboard.
I'm no concert pianist, but I'd do that last group 1313, not 1213. That requires less awkward shifting of the hand.
You might try 3413 1313 for the last two groups. A consistent pattern of finger movement like 131313 can be easier than "playing 5-finger exercises."
We can't see what comes next, but it's not obvious that 1 on the E flat in the next bar is a good idea!