Test drive concern: engine stays revved after foot off accelerator

It can be very normal, the engine will be recharging the main battery [the computer overrides the driver]
If you are driving with a very light foot the hybrid system will be using the battery a lot more ,which will eventually need recharging.

This also happens for the first 1/2 mile after any cold start up.

 

Doesn’t sound right. Whenever you step on the gas, it should accelerate

 

Mine doesn't.
At low speeds in crawling traffic, the car is driving on the electric motor only.
Sometimes the engine kicks in and starts charging the battery .It accelerates up and down with the gas pedal/ electric motor but the engine stays at a constant RPM [where it is most efficient]
The clutch only engages after a certain speed.

The other thing I didn't mention [which happens at higher speeds] is sometimes the engine is engaged to try and discharge the battery to prevent cooking it.
I've had this happen a couple of times when driving on the open road.... A couple of long downhill runs with your foot on the brake [re-gen] will try to overcharge the battery.

This ^^^^ scared the sht out of me when it first happened [and got me searching for internet answers]


The battery vents could also need cleaning.

 

yours doesn't accelerate when you step on the gas?

 

If I am parsing the wording correctly, there is noting to worry about. Most people interpret "continue to rev" as increasing the RPMs. I think that in this context the phrase meant that the engine speed did not change. This is OK in a Prius because the wheel RPM is not directly related to the engine speed. The engine speed is carefully controlled so that it runs as efficiently as it can. The excess energy is stored in the traction battery until such time that it makes sense to use the battery to power the car again.

Many people get confused when the engine speed increases as they are holding the car speed steady, especially when going up hill. As result they take their foot off the gas pedal to "keep the car from over revving". The proper way to respond is to hold the speed steady and trust that the ECU will never let it over tax the engine nor the electric motors.

I think of the gas pedal as providing a suggestion to the ECU that you want to go faster or slower. The ECU then uses the resources as needed to move the car at the desired speed.

 

Some of that description of how the car outwardly behaves is about right, but it's better to remember there is no clutch at all. The engine is always engaged to the transmission, and the engine's torque is always split to MG1 and the transmission's output in a ratio that never changes. (Power, by contrast, is torque ✕ rpm, so how much of the engine's power goes each direction is under computer control, through the rpm of MG1.)

Again, a pretty good description of the car's outward behavior, but it would be better not to say the car ever tries to overcharge the battery. It doesn't; it is programmed to know the battery's limits and make sure it never exceeds them. (In a similar way, sometimes new owners worry that the car might overrev the engine in some circumstance or other. It won't; again, that's under computer control, and you can sometimes watch it take the engine right up to the max programmed rpm, but it won't go higher.)

When the engine is heard revving on a downhill, it is not so much trying to discharge the battery, as simply providing a place for the energy gained from gravity to go, instead of being sent to the battery at all. The energy is just used to twirl the engine around, with no fuel or spark and a closed throttle, making it do the work of a big vacuum pump.

If you are at the top of what you know will be a long descent, you can select B mode, which pretty much just tells the car "hey, this is going to be a long descent". The car will then further reduce the amount of regen power it would normally direct toward the battery, in favor of doing more engine twirling than it normally would. That gives the battery a more gentle charge, which will probably fill it to the target level by the end of the long descent anyway.

 

The Prius you drove in the early 2000s probably had the same 1.5L engine that's in the C. The CVT has been modified a bit since then and the horsepower rating is slightly lower in the C. What you noticed on the backroads in the 30-40 mph range in terms of the engine continuing to rev a few seconds after letting up on the gas I believe is normal. I have experienced that as well. But I do not recall ever hitting the pedal and having the car not respond right away. The response might be quite leisurely depending on the circumstances, but there was always "something" there.

The computer does control things in a fairly rigid manner to maintain hybrid battery life. Toyota certainly doesn't want to replace your battery under warranty, so it keeps it from completely discharging and fully charging to make it last as long as possible. This can result in some odd behavior for someone not used to it.

To ease your mind a bit I would do the following: Get a maintenance history from the owner. Try Car Fax for what occurred with the previous owner(s). Check the cleanliness of the hybrid cooling fan filter under the rear seat. If it's clogged, that's a red flag. Also, testing the hybrid battery with the Dr. Prius app is a good idea if the current owner will oblige you. Hybrid battery diagnostic and repair tool for Toyota and Lexus. Having this info should help you make a decision.

 

The way you described this; kinda sounds normal. I had a 2012 Prius C. drive-by-wire system, CPU controls idle speed and your traction battery was probably way low after those hill climbs. The motor remained at a slightly higher RPM to recharge the traction battery to minimum allowable set point. The car did increase speed, but you had to use more accelerator pressure - that's typical in Eco mode. The power split in the transmission and CPU makes the car a bit lethargic. If you switch to normal or sports mode; that will go away. The pedal feel, not the occasional higher engine rev.. You may also want to check if the throttle body has ever been cleaned.

Hope this helps...

PS, ask the guy selling it - if he's ever changed the ATF.

 

A healthy Prius can do this. If the computer decides that the hybrid battery is both too full and too warm for its liking, it will use the engine as a dead load. No fuel is being burnt, it's just the electric motors forcing the engine to spin in order to draw down the battery a bit which also paradoxically cools the battery slightly. This is done to help achieve the longest lifetime for the hybrid battery.

A thing to get used to in a Prius is that the computer runs the engine as much as it wants, at the RPM it wants, whenever it wants. And also just spins it electrically sometimes because it feels like it.

The battery ECU can decide that you've reached "too full/too hot" status more easily on a tired old battery pack, but this isn't a very specific metric because again- there are circumstances where a healthy new one will do exactly the same thing.

 

"when i put my foot back on the accelerator, it seemed reluctant to increase speed"

 

So if the car was still rolling and you get on the pedal to increase speed? Many new Prius drivers are surprised by how much pedal is needed to accelerate from a lower speed to a higher speed vs. starting from a standstill.

Our c will leap off the line, 0-15mph is a very quick acceleration. But 16-80 is far, far slower. Been that way since new, and roughly matches my prior experience in older rented Priuseses. So I put that down to OP's unfamiliarity.

Driving a c in modern American combat traffic means you will be completely flooring it at some point on nearly every trip. Just the way they are. Don't be shy with that skinny pedal.

 

Hybrid battery temperature was likely high