Add the oil to the instant pot, making sure to cover the bottom of the pan.

Dredge each stewing beef cube in the flour, making sure to coat each side. Shake off the excess flour (don't add it the extra flour to the stew, just add the floured meat).  Then add the beef to the instant pot.

Add the onion, tomato sauce, beef broth, salt, pepper and sugar.

Use the manual setting on the Instant Pot, and set it to 20 minutes.

After this time, vent the Instant Pot, then open when it is ready, and add the vegetables (celery, carrots, potatoes). Give the mixture a good stir.  NOTE: If the stew looks too dry, you can stir in 1/2 cup more beef broth.

Use the manual setting again, setting it to 15 minutes.

Once the stew is done, let it rest for about 10 minutes in the pot before venting.