2012 Prius Two. Cylinder misfire P0303.

these fuel injectors from corolla should work fine since the motor in prius is from corolla, exact same motor.

from what your story is, i can almost be sure its head gasket thats what my issue was. is tarted getting cylinder misfires on 2 cylinders and started loosing coolant. from few rough startups to eventually every single startup was rough and when i tried pressing gas pedal all the way immediately after start then i wudnt get knock since the coolant would be pushed from chamber instantly. but my head gasket was in pretty bad position, you should get boroscope and check your cylinder for any traces of liquid. also if your head gasket just started failing then coolant level may not drop dramatically. but every single prius will have head gasket failure at some point thats what everyones agreement is on. you should clean egr cooler and valve for sure regardless if your head gasket already failed or about to fail. that was what caused my head gasket to fail.

 

You want something equivalent to this. Link is for Prestone brand, or you could get Toyotas. Make sure it's 50/50, not full strength.

"Extended Life", the pink stuff, for Asian vehicles.

 

Are you coolant shopping just because of the EGR cleaning? It can be done without spilling a drop. Here's some info:

The simplest way to see where you're at, is to check the degree of carbon build up in the EGR pipe, a stainless steel connecting pipe between the EGR valve and intake manifold. Watch @NutzAboutBolts video #16 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

Two or three other videos linked there too, for the full cleaning of the intake manifold, full EGR clean, and Oil Catch Can install.

Good thread:

EGR & Intake Manifold Clean Results | PriusChat

Another:

Oil Catch Can, Eliminate that knock! | PriusChat

Some tools worth having:

E8 Torx socket (mandatory)
E6 Torx socket (optional, but good to have, to remove the throttle body studs from intake manifold)
3/8" ratchet wrench, regular and long handle, flex head, you can never have enough (or 1/2 plus reducer)
1/4" ratchet wrench, or 3/8" to 1/4" reducer
Ratchet extensions: you can never have enough
Long needle nose piers, straight and bent tip
Ratcheting 12mm box wrench (optional, but makes disconnection of the EGR cooler from exhaust easier)
Torque wrench (3/8" and 1/4" both good to have)
Floor jack and safety stands (or ramps): basically some method to raise front, if you need to take underpanel off, which you may need to, both for access and to recover dropped items.

Comment regarding clamping of coolant hose, mentioned and or shown in videos:

1. When removing the intake manifold for cleaning, you do need to lift the throttle body off the intake manifold. Still, the coolant hoses connected to the throttle body have ample slack, enough that you can leave them connected, and just tie the throttle body to something adjacent, say the inverter wiring harness.

2. When removing the EGR cooler, removing coolant hoses is necessary, but if you drain 2 liters/quarts from the radiator drain spigot prior (into a clean container), the coolant level in the system will be dropped below the EGR componennts, and you won't spill anything. Just be sure to not tip the cooler when lifting it off (and catch the rear gasket): there are a few tablespoons of coolant trapped at the lower back corner.

Pour that into your previous drained coolant, and when done pour it back into the reservoir. If you've got the coolant bleed bolt (2010, 2011 model years), leave it open while pouring the coolant back in, till coolant starts coming out. For later model years, leave the topmost coolant hose on EGR disconnected till coolant starts coming out. Also, might help to burp the main radiator hose as you pour the coolant back in.

 

Watch @NutzAboutBolts video on the engine/inverter coolant changes, if you haven't already (links in a thread pinned at top of this forum). More info attached: