2011 Prius severe hesitation 3-4 times a year

complete guess, because those symptoms are so odd. but i'd start with a look at the egr

 

How low on gas is your Prius when this happens?

Ever run it out of gas?

What kind of fuel do your purchase?

 

Nissan had a big problem with these exact symptoms a few years ago and it was transmission. Class action and recall.

Does this happen only at a stop or when attempting to accelerate while moving?

Does the ICE "rev up" but the car doesn’t accelerate (trans) or is more of a delay to rev the engine (throttle sensor issue).

 

Time to check your fuel pressure / probably change your fuel pump, buddy.

 

Whoa whoa whoa, pump the brakes there, Paul Walker... Have you checked the MAF sensor? There are some other things that can be checked, before assuming the fuel pump is bad. And by the way, when fuel pumps go bad, they don't normally act up a few times a year. They act up, and stay that way.

This could also be a coil that gets wet after rain or inclement weather, and becomes marginal until it dries out. This would happen on my last Gen 2. I replaced the coils (the car had 212,000 miles, it earned it) and that solved the problem.

More troubleshooting is required.

 

Try cleaning the throttle body too. Don't spray carb cleaner directly on it; apply to cloth or q-tips and wipe it in.

If you want to clean more thoroughly unbolt and lift it off (coolant lines still attached) and clean it from both sides in your hand. If you want to go that route I can post torque value info.

And the aforementioned EGR, start by checking condition of the pipe running from intake manifold to EGR valve.

@NutzAboutBolts has helpful videos on both these maintenance items.

Addendum: throttle body bolt/nut torques in (added) attachment. A 3/8" or 1/4" drive torque wrench is best; pretty low values.

 

If running it past empty that much, it can be the fuel pump.

Here's a shot of our old 2010's at 199k miles and not run low on gas and only top tier fuel:

What did you do to ur Gen III Prius today????

I'd say it might be time based-upon what you describe above.

 

No wonder I drive in fear and monstrosity, mine isn’t a package 5!!!

 

Both running the gas really low and overfilling can be detrimental. It's also kinda irrational: I know it feels good, to see how far you can get on a tank, but it doesn't improve your mpg. I would just fill up whenever it's "comfortably" low, and stop pumping the first time it clicks off.

 

Glad you're not in Florida!

 

Running the gas low may mess up the fuel pump, draw up dregs from the bottom of tank. Or hey: leave you stranded...

Overfilling may foul the evaporative emmision controls. Extreme overfill, you may start spilling gas when you take corners.

 

Motor stops because car ran out gas faster and or shorter than the distance to empty predicted and your car becomes a barrier to be driven through. Your evap canister fills up and you pump 12.5 gallons thinking you defied physics, then get a CEL