My wife's 2012 Plug in Prius mysteriously starts the engine under these conditions: leaving home with full charge, she goes down a 650' long drive on a modest hill, maybe 15 -20 mph, touching the brake as needed to keep the car slow enough. Engine will fire up when the car hits about 12-15 mph. If she rides the brakes enough to keep the car below 9 or 10 mph, it won't start- upon reaching the bottom, she then accelerates modestly (maybe 35 mph tops) on the level and up another long, modest incline (all private lane, not public highway) and engine still doesn't start. Once on the road, EV works fine up to suburban highway speeds. Only when the battery is discharged does the engine then cut in normally. Not having her patience, I just put the car into neutral and let it roll, maybe to 25 mph, then slip into D when it hits the level, thereby avoiding starting the engine. She claims this "starting" problem started just after we got new tires (same size as OEM, but different brand. Seems like a programming issue, dealer was clueless.
it is usually because the freshly charged battery can't accept anymore charge. and usually as temps drop. where are you located? btw, there is no such thing as 'engine starts when it shouldn't' with pip. toyota states that it can start any time for many reasons. they just won't tell you all the reasons. did it just start doing it? how long have you owned it?
If you just don't charge it all the way it will be fine. It's engaging the engine as a brake. Just like putting it into B mode and going down a hill. I noticed it will engine brake when using the cruise also at slower speeds too. LG-H918 using PriusChat mobile app
Car is owned from new, 4 years or so. We live in Maryland, and the weather doesn't have to be cold for this to occur. We know that B will cause it to start, so we avoid that under these conditions. And yes, it begins with a full charge, after overnight. Seems to only happen on our drive, not otherwise... but then, it is her car, so I really don't know. As I had noted, she claims that this wasn't happening before we got new tires last spring, but I can't logically make a linkage. I don't like driving it all that much. (Subaru Crosstrek and Mazda Miata are my rides)
what are the tyres pressure? who installed them? i wonder if over tightening the lugs could affect anything? i'm grasping at straws.
As stated by Matt, the car freewheels the ICE to bleed excess charge from downhill regen. Once the overcharge potential is gone (at the bottom of the hill), the ICE will stay running until the cat is warm, due to EPA requirements I believe.
Thanks, guys. I am starting to think the full charge, no place to put that new electricity might be the answer. I will ask her to brake with more force. What's confusing here is that if she keeps braking the car (and showing regen.) to keep the speed under about 9 or 10 mph, the engine doesn't start! The tires are set at 3 lbs over what the manual states. Any more and the car bounces over bumps, although when it came home from the dealer, they had set them at the sidewall's max. pressure! Might help the mileage, but gives a ride that makes a track car feel mushy.
couple things don't make sense: the fact that it didn't do it for the first for years, and then, only after you put new tires on. and 2, that it is doing it at that slow a speed. what kind of road allows for 15-20 mph?
Ah, the "road" is a private lane, one car wide, going down thru the woods and over the stream. So going, say, 40 mph would be really pushing it! Like I said, doesn't start as long as she keeps it below 11-12 mph, but does if she goes 15 +-. Doesn't then start when she drives up the hill at normal speeds, maybe 25-30 mph in EV, or when she pulls out onto the main road and accelerates to 50 + mph in EV. And no, I don't think it started on the hill for the first 3 or 4 years- same situation, otherwise. Tires are Michelin Energy Savers.
The PIP definitely seems to get touchier when the temp dips to around 40F. A nearly full cold battery just doesn’t seem to accept as much braking charge as a warm battery can. Even though my first hill is ¾ mile away, and only moderately steep, the engine will kick on if I brake too hard from 35 mph or slip it into B. I think your new tires, pumped up hard, are giving you noticeably less rolling resistance to the point where your wife’s car draws less power to move and requires a bit more regenerative braking to stop. That could kick the engine on sooner to prevent overcharging.
My 2015 PIP did the same thing your wife's car is doing, and every time. I believe going down the hill with a fully charged battery which couldn't take more regen was the problem. Yes, keeping it below 10 or 12 MPH avoided the problem, and I believe that at that slow speed there was not enough regen to cause the engine to start. I usually avoided the problem by using N and the friction brakes at the bottom, where I had a stop sign. My new Prius Prime goes down the same grade normally in EV without starting the ICE.
agreed. the question then, why didn't it do it for the first 4 years? perhaps pluggo nailed it with the tires in post #10.
I think so, too. Probably the Michelins have less rolling resistance. I wonder what the previous tires were and how much pressure they had.
