Engine Knocking/Shaking During Startup on 2012 Prius

I have the 2011.
You would think the 2012 would come with the new TSB part applied to correct the old problem. Strange?

I my experience last winter I used the Heet additive every other gas tank and I never experienced it again. The winter was mild on the east cost so that must of helped. I also tried to use the medium, or high grade octane gas.

I'm at 20K miles and it only happened 2 times on cold days. This happened after I did not allow the warm up cycle to finish the night before.

Maybe bad gas or water from condensation in the system?
Keep us posted with what you find out or try.

 

The '12s should have the new intake manifold design, so shouldn't have the problem.

How would you describe the humidity at the time of the episode?

 

So it went from the drive way, where it was washed, then you moved into the garage a short distance?
The ICE never warmed up and shut off on it's own, if this is true.
my2cents.

 

Welcome to the knock club.

I would report it to the dealer though so that they can document it. There is a slight possibility it left a code they might want to diagnose.

 

One other member reported bad gas from BP was the cause, BTW.

 

I've found that if I let the car warm up to the point of ICE shutdown after washing the car with a cold engine, the rough start won't occur.

 

When in doubt, let it warm up. =)

 

The only time I have start knock is when I forget and DON'T do this. I've learned to just let the car run for a few minutes unti the ICE shuts off if I need to move the car around the garage / driveway. I try to plan ahead so I don't need to move the car short distances. If I'm going to wash it, I leave it outside and then use it for an errand after washing the car. I also keep it on the side of the garage opposite my tractor so I don't have to move it to mow the lawn / plow the drive.

All vehicles have quirks. While this is annoying and possibly damaging to the engine, it seems that it can be avoided.

 

Yes, avoid interrupting the warm-up cycle.
or:
Preferably, use the EV mode for very short distances.

See also for example: Can I start and move in EV mode? | PriusChat

 

That is a very typical dealer response. Once the manifold clears up and the car stops shaking all sensors appear to respond normally by the time you bring it in. That's why the dealer can't find anything.

The TSB is only being done if the dealer can actually see it happen. Some dealers are nicer and take your word for it along with a video recording of your car shaking.

Since you are new to the car and now know what to look for, be more aware of it when the temperature drops.

 

Chances are some water spray got inside and caused engine misfire for a few seconds, but not long enough to throw a code. I would not sweat it if I were you.