Prius downshifting or slowing down on small hills. Also bucking, or jerking some.

Welcome to PC.

The first thing you will find is that service departments only operate on the basis of diagnostic trouble codes, and then use charts after that to replace parts until the codes are gone. So if your car has no codes, then it is perfect and there is nothing they can do.

I would check for alignment issues and brake drag. Take off the wheels and make sure all is well with the slide pins (corrosion, grit, etc), and see if each wheel spins freely. An alignment shop will run a test for a small cost, and you can post the results here to determine if it is too far out. Check your tire pressures, they can be 40 psi or more for best coasting.

Make sure you are not in B mode on the shifter. Always use D unless the hills are long and steep. Also, make sure the engine is shutting off when you are gliding. If the engine is staying on, which can happen due to a problem (like a failed 12V battery) then the car can have that laggy feel.

 

I wonder if the plugs were ever changed?

 

Tire pressure
Spark plugs & while in there ignitor tip corrosion inspection
Throttle body clean
Tran fluid change
Inverter coolant change

 

Lee, it sounds like you're driving in "B" mode instead of "D" mode on the transmission.

 

I think on some really long, steep descents, I've had the engine rev up almost as if it were in B mode. I believe that even in D, when the traction pack reaches maximum charge, the system might use some B-mode behavior to bleed off electricity. This probably wouldn't happen on slight hills though. Does the speed of the gasoline engine actually increase as you descend (you can tell by the noise/vibration), or is there just a feeling of resistance?

 

That is indeed the case. If the descent is long, the engine will be completely off, but will start revving when the battery fills. It does not rev as high as when B mode is selected, however. In fact, I have taken to using B mode much less, as the 4000RPM produced seems just too frantic for the small increase in drag produced. I think in the long run it is easier to replace the brake pads than the engine.

 

Yep, D mode doesn't start revving the engine to burn off excess charge until it's right up at the very top level of the 8th bar. In "B" mode it basically spins the engine all the time, but really starts turning up the revs to a noticeable amount when the SOC is in upper region of the 7th bar. It seems to progressively increase the revs as you go from 7 to 8 green bars.

Yeah it can really get that little engine screaming on a long descent, that's for sure. It can be pretty disconcerting the first time you hear it.

Despite that I'm using "B" mode more than ever for long descents these days, because I think it makes it a bit easier on the HV battery and mine is definitely showing it's age. I think my engine will easily outlast the HV battery.

 

OK uart. Using Priidash and watching charge amps, I see that in either of the two modes, the charge current goes to very low values when the charge is at all green bars. The only difference is that there is a need to use more friction braking in D mode. So one or the other does not make that much difference on the battery. Even if the shift is made to B mode proactively, at the top of the hill, then the battery still gets to the same level of charge. At least here, where I go up and down 1000m in elevation each trip.

 

Yep, if the descent is large enough. Around here the hills aren't that large (well at least most of them aren't) but there's lots of them. My battery gets some funky behavior (undershoot) after the battery has been charged to 8 bars, but it's usually ok if it's only 7 bars. I actually use "B" mode to prevent me getting all 8 green bars on the modest sized hills where I drive.

BTW. With this undershoot the battery ECU gets confused or something about the state of charge. After it goes to 8 green bars it (soc) stays high for a quite a while, but then suddenly plummets to 2 or 3 bars with virtually no discharge occurring. It's really annoying and I often think this battery can't last too much longer, though it has been this way for nearly 2 years now and is still going.

 

I wonder if a battery module would go bad if you let the car sit for a couple weeks? like a weak 12v that sits for a period of time.

I worried about my 2005 going out, couldn't take the suspense anymore, bought myself a newer battery and replaced it today. Mine doesn't undershoot but the time factor was making me nervous

SM-N900P ?