ICE runs rough as is shuts down

the shudders

I called the dealer this a.m. about the very same thing. Thought maybe I'd get more answers here.
I was hoping that it was due to the car having low mileage, perhaps a small adjustment needed somewhere.
I'll write again if I find anything different than what I'm seeing here.

 

Hey, this happened twice to me yesterday. My daughter has an 04 Prius and the first time I drove it I was surprised when it "shut off" at a stop sign. But the shut off was smooth.

But when I stopped yesterday, it didn't feel like a "shut off" like my daughter's car did. It sounded and felt like it was "stalling" or maybe even "running out of gas" is a better description.

It was very rough and shuddering.

The only times I felt it was when the car was cold. But from what I've read here, it's not supposed to even shut off when it's cold.

My Prius has 254 miles on it and my average per the screen is 53.9 MPG.

 

I guess I misunderstood when some were talking about the various modes like s1 and s2 and stuff.

I thought it had been said that when the engine is cold, the engine would stay on at stop signs until it had reached operatiing temperature.

I didn't mean that it would stay on when the weather was cold, only the engine was "cold".

Sorry

 

In stage 1 it will not shut down. Stage 1 is fairly brief. A bit warmer, it goes to stage 2, and will shut down any time you stop. A bit warmer and it's in stage 3. Now, paradoxically, it waits longer to shut off, and does so very roughly. A bit warmer still, and it's ready to go into stage 4, but will not do so until you come to a stop for 5 or 10 seconds. After that, shut-downs are much smoother, though you can still detect them. However, in stage 4 (and sometimes in stage 2, I think) it will shut off before the car has come to a stop, so there will be nothing to feel when the car does come to a stop.

In all 4 stages it can run on the ICE alone, it can run on ICE and electric together, or it can run on the ICE and recharge the battery. In s1 and s2 it cannot run on electric only. In S3 it can run on electric only if you have gone over some speed (around 35 mph, I think) but if you slow down and then apply the brake, it will not go back to electric-only until you speed up again, or get into S4.

What mystifies and upsets me is why it should require a full stop to go from S3 to S4. S3 is inefficient, because, as near as I can tell, it won't stop unless you come to a full stop. However, if you have the EV switch you can engage EV mode while in S3, and that's some consolation (not sure about S2, but I think not).

 

It's not smooth anymore! At least not as much as it was. I've noticed that the more I coast to a stop sign, the more shuddery the stop is. I think you just notice it more when the stop is gentle.

 

i wonder if some of the colder areas in the US have changed the gas formula? that might have something to do with it.

 

If we are speaking about the shut-down shudder, I have noticed no difference from winter to summer. And as far as gas, it seems unlikely they'd have changed to winter formula yet.

 

im sure they havent changed in my area since ive seen no change in my mpg, but i was surprised to read that some formulas of gas freeze at 40º F. that temperature is not out of reach in some areas at this time i would think. although there is supposed to be 43 versions of summer gas and 21 version of winter gas so i dont know. with so many varieties, i wonder if anyone has "autumn" gas...

 

At 14,000+ mine still does it, mostly when I first get in the car to drive it. It does it as much now as it did when I first got it. Here's a link, this subject was brought up before: http://www.priuschat.com/forums/viewtopic....=922&highlight=

 

Using the EV button to force the engine to shut down doesn't really help, the engine shuts down, but at the first opportunity it comes back to life. I dislike S3 as well. It's hard to coast and even then the engine keeps using fuel. And having to stop to go from S3 to S4 is strange as well. Going over 90 km/h seems to put the car in S4 as well, although I sometimes stop the car for 10 secs anyway, just to be sure. S3 hurts my mileage.

Strange thing is that at the end of my commute, some 90 kms highway, the engine seems to be stuck in S3. When I drive through the down where the office is, I cannot get into full electric mode and when I let go of the accelerator and there are green arrows there's still some fuel consumption. Only if I do the full stop thing (10secs) the engine shudders a bit and shuts down reluctantly.
The speed limit is 120 km/h over here and I put 123 km/h on the speedo and keep it there using cruise control. So I think the car should be in S4 when I drive into town. This doesn't always happen, but I've noticed it a few times.

Also sometimes the car seems to be in S4: electric mode is easy to get, coasting is no problem, engine shuts down at the traffic light. But when I accelerate abruptly and have to break suddenly due to traffic, the system seems to get confused and puts the car back into S3 it seems. Only a full stop (10secs) seems to resolve this. I'll mention it to the dealer I think.

/me scratches his head

 

Batavier: What you are describing is frustrating, but is the normal operation of the car:

It will not go into S4 until you have stopped for 5 or 10 seconds after the ICE is warm.

If you exceed a certain speed (I think it's around 35 mph, but not sure) it will function as though it was in S4, and you can then slow down and it will still act as though it is in S4. But as soon as you apply the brake below that speed (even if you don't stop!) it will be back in S3.

Thus if you get on the highway without having reached S4 (maybe the engine was not yet warm enough, or maybe you have no long stops before the highway) the car will function on the highway as though it was in S4, but once you get off the highway you are still in S3, and will remain in S3 until you stop for 5 or 10 seconds.

Sometimes it's 5 seconds, and sometimes it's 10 seconds, and I have not been able to figure out what conditions govern that distinction.

You can go into EV mode from S3 (not sure about S2) but when you exit EV mode you will be in whatever mode you were in when you entered it. EV mode "helps" in that it will draw down excess battery charge, but it does not help get you into S4.

I repeat that I am mystified and upset that the car won't just go into S4 as soon as it is warm enough. Why require a full, long, stop? I wonder if this isn't a bug in the computer code.

 

ya mine does the same thing SOMETIMES... a few times i checked the charge level and that doesnt seem to make much difference either. (although my charge range is almost always in the middle blue range)

the car seems to not be very consistent in how it operates sometimes.

 

I have decided to start refering to S3a and S3b. S3b is the stage it's in when it's fully warm and you have exceded the trigger speed that allows it to function as though it were in S4.

S3b and S4 appear to be identical, except that if you apply the brakes while in S3b below the trigger speed, it will go back to S3a. Only by coming to a full stop for 5 or 10 seconds can you get it into S4.

S3b is sort of a temporary S4, which gives you full hybrid operation at highway speed. Only in city driving do you need to get into S4.

In S3a it will keep running for several seconds at a stop, will not stop if you merely lift your foot off the pedal, as it does in S4, and in S3a it shudders noticeably as it stops.

In S2 it stops more readily and more smoothly than it does in S3a.

 

lately ive noticed a shudder if i have just done say 30+ miles on the freeway and stop quickly after exiting the freeway.

the more i think about it, the more it feels like a normal engine dieseling after shutoff when the engine is hot. except in the Prius' case, the shudder results from an engine still turning from momentum after fuel is shut off.

 

For the second time I have had a major shutter at a stop. The first time I would guess that the car was warmed up. The second time today I am sure it was fully warmed up. I got to a stop and it was if the ICE was "dieseling" I pushed harder on the brake and there was a third shutter and "finally" it shut down. Both times I was going up a hill of fair size and had to stop at a light same light actually. Did the up hill thing have something to behave in this way. Mostly Belle is a very nice polite car that dose not behave in this way. Any thoughts.

 

ya one thought... dont worry about it, its something that is normal, you cant change it, and it aint hurting your 4 wheel honey.

 

Henry: If it was your first full (10-second) stop after the car was fully warm, then it was precisely the thing I've been talking about. With the car in S3a it will be very reluctant to stop, and will shudder. Once it stops completely, and assuming it was warm enough for the transition, it will then be in S4 and will not shudder any more until the next time you start it.

 

Could very well be. My commute is a 1/4 mi at 25. 1/4 mi at 40. 4 miles at 50 with a roundabout to 40 and a turn to 35 down hill at 40 to the stop in question. If I make the turn at 40 to 35 and do not have to stop the first stop is at the light in question. Otherwise I might have to stop at the roundabout or at the 35 to 40 light. I will observe further.