Awful misfire on cold start

engine was stopped early before cycling therefore gas hydrolock

 

That does NOT match the story that he supplied.

Could be a leaking head gasket.
Could be an injector sticking partially open.
Could be oil accumulation in the intake similar to what other models have with the PCV problem.

If everything is working properly, stopping the engine "early" should NOT cause any problems.
I do it often.

 

When the first 2010s began doing that, a thread was started (as early as November 2010!) to document it. That was the 2ZR, 1.8 liter engine, of course:

1.8L starting rattle, knock, events | PriusChat

Very early—within the first week of the thread—a pattern had been spotted where the problem was worse if, the last time the engine was started, it ran only a short time and was shut down without warming up.

It took Toyota until January 2012 to issue a TSB for it, and what they had done was revise the intake manifold, reportedly so condensed water in the EGR passages would not be slurped into the engine so easily.

That old true story has been circulating around on PriusChat and picking up different variations in different tellings. Sometimes the condensed water turns into gasoline, sometimes it's the goop under the throttle body, sometimes it's causing hydrolock instead of misfiring, and so on.

I don't know whether the 1NZ engine in the c is susceptible to the same sort of thing, but that old story is probably what post #2 was getting at (with water turned to gas, and misfiring turned to hydrolock).

 

I've had one knock on cold start, and it was a day or two after doing a very brief driveway start up. I've played it safe since then, and there's been no repeat.