P3191 And p0300-p0304

1. When was the last time the iridium spark plugs were replaced? If more than 60K miles have been logged, replace them with the correct NGK or Denso plugs now.
2. While the plugs are removed, inspect the spark igniters for burn marks, cracks, or rust deposits on the plastic body. Replace any igniter that has a problem. If you see rust, this means that water got into the spark plug well. That would cause misfire in that cylinder.
3. Remove the mass air flow sensor for cleaning. Use the correct MAF cleaner spray.
4. Clean the throttle body interior and throttle plate using throttle body cleaner. Use the minimum amount of cleaner, ideally by spraying the cleaner on a cloth and using that to scrub away at the interior and throttle plate. You would need to remove the air cleaner housing for access.

 

Patrick has excellent points, and I would add, think about fuel quality... when did you last fill up? If the tank was nearly empty, and the vehicle has sat for a day or so, it's possible that the ethanol in the fuel has soaked up enough water from the air that the prius is having a hard time combusting what it gets.

Your profile doesn't say where you are, or whether it had been raining / snowing when this occurred...

A bottle of Techron prior to the next fill, preferably at a high-volume station, of good quality fuel (premium, if you can afford the price delta) will also do wonders.

 

I doubt that the gasoline engine has actually started. More likely, MG1 is just spinning the engine which has not started.

If you want to verify that the engine has started, see whether it responds to the accelerator pedal. If it does not, the engine did not start. Or, shift into N while the engine is "running" and see if it continues to.

What do the spark plugs look like?

When was the last time that the car operated correctly?