After a hard (not harsh) acceleration and letting up on the gas pedal the car slowly revs down. This does not affect performance and no codes are showing. Any idea what could cause this and if it will lead to other problems? This is a 2010 with about 280k miles.. SM-G960U ?
Does this happen all the time or after a longish drive? If it is after a long drive or in hot weather I would suggest you check your high voltage battery temperatures because at high temperatures the car will reduce the amount of regen braking that you get and this may cause the engine to "freewheel" a lot more because it will have nowhere to send that excess energy. Also check the cooling fan for clogging etc.
? This is normal.... Less air and fuel caused the engine to slow.... What problems would you think this would cause???
I noticed this when I first got my prius. Going down a decline and releasing the gas pedal, would show possible mpg of 100 but then the ICE would rev and rpm would go up randomly and you can see the mpg go down when it does that, even when I am not using the gas pedal. I then thought well lets change the trans fluid and that issue went away. It has been about 5-6 years since and I think the issue is coming back. I will be changing the trans fluid again and see if the issue is resolved.
This is on flat ground. I've had the car stop charging coasting downhill when the battery charge tops out that i think you are describing which is normal. SM-G960U ?
I forgot to mention that my traction battery has been having issues with coding for replacement when I drive at low speeds and end up using the bybrid drivemore and I keep clearing it and it continues to drive with no problem and this is not happening in concert with the revs SM-G960U ?
Well it should still be clean, but check for a sticky butterfly valve. A bit more difficult on these drive by wires.
Well that'll interfere with engine idle - ICE ECU keeping it high trying to recharge traction battery.
You had only given partial information. It's like telling the doctor you hurt. But don't tell him where, and how bad..... Since you're having issues with the hybrid battery, that changes everything.
Your Hybrid battery is the issue. Sometimes at low speed the battery charge level will just tank down too quickly and the ice only kicks in when its around 25% state of charge instead of the usual 39%. At this point if voltage differences between adjacent modules is not too great you wont get a code but your vehicle will reduce charge power to around 3HP instead of around 23HP and discharge power to around 2HP instead of 20HP. This state will slow charge the battery until its around 70% and will keep ICE running until you cycle the car OFF and On or you clear battery codes with scan tool, You normally will not get EV mode in this state. In this state your charge while driving is low and regen is very low. This is the reason your revs take so long to die down because the car is not converting that energy to electrical power for the battery at a high enough rate. The same "derating" happens when the battery is too hot (or too cold, though I have not experienced this personally) Side note: the quoted HP values are for the Prius C, but I believe they explain what is happening.
I would say this behavior is one of the "no problems" you're getting from a traction battery on its last legs.
