Multiple misfire, checked/replaced the usual stuff

I'm guessing if you replace the injectors you already cleaned throttle body and mass air flow sensor?

Also have you rebooted all the engine computer settings by disconnecting the 12v battery for a few minutes?

Also being super low on engine oil creates vibrations in crankshaft that triggers misfire error codes. So might want to figure out some ways to look into the overall health of the bottom end.

 

I would be looking at data on a scantool- specifically what short and long term fuel trims are doing at idle, and then while at cruise. I would also "add fuel" to the engine at idle to see if it affected the misfire. You could use a propane "enrichment" tool to feed propane into the air cleaner inlet- a propane torch might work but doesn't flow much fuel.

Another possible cause could be a valve problem. A broken valve spring or valve intermittantly not seating can cause a miss but have good compression readings. An old fashioned vacuum gauge connected to intake manifold source such as the hose to the purge valve can help.

What were your compression results for each cylinder?

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If you've done all these things and never disconnected the 12v battery to reset all the engine's settings yet, I suspect that's going to resolve it. Every time I've done same kind of work on a Prius engine it runs like it's going to die unless I reset everything by disconnecting the 12v.

 

Roaming misfires is usually blown bottom end of motor. Main bearing has failed causing subsonic vibration.

Or on a g2 usually piston. This engine likes throwing the #2 piston out the side of the block.

Vibration distorts the pg waveforms from cam & crank sensors and
The engine ecu gets poor waveform signals it cannot decode so defaults to random multiple misfires. Very common.

Usually from poor oil maintenance. Tough little motor just has to have all its oil or the motor has had the shit beat out of it.

put engine in inspection mode so it idles nonstop then crawl under the front of car and listen to the bottom end. Should be pretty definitive under there.
Go on YouTube look up. PRIUS INSPECTION.

Lots of engine replacements on this forum.

 

Back when I owned a vehicle that required a propane enrichment tool as part of its carburetor adjustment procedure, I found I could unscrew the restrictive orifice from my basic hardware store propane torch, and that made the flow adequate to the job.

It is good to remember to put the orifice back in before using it as a torch again.

 

I doubted bottom end failure on my well maintained 2008 too, my misfire problem sounds very similar to yours, but was only on 1 and 3. Mine intermittently rattled/shook at idle, it would idle fine if I feather touched the gas pedal or put it in Neutral, both I assumed disengaged the load of the inverter/charger generating power. 4 refurb injectors seems to have fixed the problem, but I also cleaned the TB and MAF.

The fact that you replaced most all of the items and that all 4 of your cylinders are reporting misfire should point to something common to all. Assuming it isn't the ECU or wiring or ground problem, could it be a failed fuel filter that fouled all of your new OEM injectors?

 

Did you ever resolve this issue?