I bought a new 2014 Prius plug-in base model two weeks ago. No problems until yesterday. The engine has started revving really loudly on occasion. It's much louder than the normal ICE noise in hybrid mode - 2 or 3x as loud (much louder than our regular Honda Civic engine). When the revving happens when I'm in EV mode, the EV mode light on left side of dash stays on (but it's clearly not in EV mode). The EV and Eco symbols above the power bar go blank. The MPG won't go above 25 mpg, no matter if I'm not touching the accelerator. Switching from EV to Hybrid mode and back does nothing. The only way to get it to stop is to stop the car, turn it off, turn it back on, and then it's fine - EV or Hybrid mode, it sounds normal again. I have not tried to drive more than a mile with the noise to see if it goes away. It occurs when: If the fan, heat or defrost is on when I turn the car on - turning them off doesn't stop the revving. If I switch the fan, heat or defrost on when stopped at a light - turning off doesn't stop it. (But it doesn't happen if I turn heat or defrost on while moving in EV or Hybrid mode.) If I switch from EV to Hybrid mode while stopped at a light. The weather is cooler now and I'm fine with the ICE starting to warm up the engine, the compartment, etc, but the revving noise doesn't seem normal. Anyone else experience this?
I have seen similar in a generation one Prius when it rebalances the traction battery. But the battery was on its last legs which I doubt yours is.
Yes the ICE will run if you ask for heat and it will not shut down until it warms up or you turn the car off; whichever occurs first. I can't answer to the revving issue without more detail.
fotomoto - It's not clear to me why it goes away when I restart the car. Presumably the engine is the same temperature and would still call for the ICE, but it doesn't...I can use normal EV mode after the restart.
What you're describing sounds like all the conditions that would trigger the ICE to start. And assuming it is cold, its in its warm up phase. Which IS much louder than when it's already warmed up. When the car is stopped, you would definitely hear it since it would continue to run and you're probably not used to hearing the ICE when the car is stopped?
When in Eco Mode, the engine will run/warm up until it reaches 130F. However, based on what John has posted here before, he said something like the heater will continue to provide heat without the ICE until the coolant temp reaches something like 100F (dont quote me on that number, but it was something to that effect..) So when you have EV range and you request heat, the ICE will start. When you shut the car off and restart it with the heater running, I'm guessing the coolant temp is not at 130F (since you shut it off before it completed its warm up) BUT its higher than the minimum coolant temp required to provide heat without the ICE re-starting.
The revving ICE is distinctly louder than the normal ICE in hybrid mode, i.e. they are two distinct sounds when driving. The best I can describe it is that it sounds like a gas generator you would hear behind a food vendor at the county fair. Maybe the engine has two modes - heating mode and normal mode. It's just a weird and loud sound for what is normally an elegant and quiet car (even with the normal ICE on).
When the engine is trying to come up to temp, it runs fast, like the fast-idle on a cold carburetor engine would do.
I think I've decided that it's related to heating or defrosting and it's the fast-idle mentioned before. I kept driving after I heard it again and it eventually went away, back to hybrid mode. Thanks for everyone's responses.
