Engine tries to stop, but won't, and cycles

[swiftyprius]

Hi, This morning my two week old Prius did something weird. I rolled backwards out of the driveway, then went into drive, heading for the school bus, outside temp is about 68. After about 1.5 miles, went down a pretty steep hill, bringing the battery to green SOC, get stuck at the stoplight at the bottom.

I had the fan running just above low, no AC, and turn it off because of the stinky car in front of me. At this point I realize ICE is running for some reason, but then it starts to cut out, but then it kicks back in, and keeps cycling until the light goes green, about a minute. Has not happened again today.

Any ideas what this could mean?

[swfoster2]

<div class='quotetop'>QUOTE(swiftyprius @ Nov 13 2007, 08:57 PM) [snapback]539196[/snapback]</div>

Hi, This morning my two week old Prius did something weird. I rolled backwards out of the driveway, then went into drive, heading for the school bus, outside temp is about 68. After about 1.5 miles, went down a pretty steep hill, bringing the battery to green SOC, get stuck at the stoplight at the bottom.

I had the fan running just above low, no AC, and turn it off because of the stinky car in front of me. At this point I realize ICE is running for some reason, but then it starts to cut out, but then it kicks back in, and keeps cycling until the light goes green, about a minute. Has not happened again today.

Any ideas what this could mean?
[/b]

Maybe the car was not warmed up yet? You could also use the recirculate option instead of cutting the fan off in order to block out the fumes from the car in front of you. Hope it's not a serious problem.....

[efusco]

<div class='quotetop'>QUOTE(swiftyprius @ Nov 13 2007, 07:57 PM) [snapback]539196[/snapback]</div>

Hi, This morning my two week old Prius did something weird. I rolled backwards out of the driveway, then went into drive, heading for the school bus, outside temp is about 68. After about 1.5 miles, went down a pretty steep hill, bringing the battery to green SOC, get stuck at the stoplight at the bottom.

I had the fan running just above low, no AC, and turn it off because of the stinky car in front of me. At this point I realize ICE is running for some reason, but then it starts to cut out, but then it kicks back in, and keeps cycling until the light goes green, about a minute. Has not happened again today.

Any ideas what this could mean? [/b]

When the SOC get's "too high", meaning at the upper range on the battery SOC the ICE will cycle like you describe off and on 4 or 5 times...the energy used to spin MG1 and the ICE drains some of the charge from the battery and gets it back down to a more 'comfortable' range.

Seems more common in cool weather, but that's probably b/c the SOC tends to be higher in cold weather since the ICE runs more to warm itself up and thus generates more energy to send to the battery.

[qbee42]

The key here is going down the "pretty steep hill", which brought the SOC up to the top. As Evan points out, the Prius will spin its engine without gas when the SOC is too high, just to burn off some of the extra energy.

Tom

[richard schumacher]

As for the stinky car, note that you can use a steering wheel button to manually set the A/C to recirculate and not suck in someone else's exhaust.

[Slartibartfast]

<div class='quotetop'>QUOTE(cheminee @ Nov 13 2007, 08:07 PM) [snapback]539201[/snapback]</div>

Maybe the car was not warmed up yet? You could also use the recirculate option instead of cutting the fan off in order to block out the fumes from the car in front of you. Hope it's not a serious problem.....
[/b]

That's what I have found. If the coolant temp is not up to the optimal level, the ICE still wants to spin for a while no matter how much the battery is charged. The time it runs seems to correlate with how warm the coolant likely is. I don't have a scangauge or anything, but generally I've found two stages. It always runs about 10 seconds after startup for about 1-2 minutes no matter what. If I sit in Park and watch the energy monitor, it will charge the batteries for a while, then the tone of the ICE will change and will stop charging the batteries. If I put it in gear during this time, the ICE will shut down but start back up above 7-8 mph for another period of time no matter if I otherwise would be coasting or gliding.

Near our old place in Los Angeles, we would pull out of our garage and turn onto a four-lane street with a slight downhill grade, a 40 mph speed limit and no traffic light for about a mile. On days and times with little traffic (rare), I could pull onto that street, accelerate to 40, keep light pressure on the <strike>gas</strike> accelerator, and glide down to the light. But I found that, if it was the first trip of the day, the ICE would still be spinning as I slowed to approach that light, and I would not be at 99.9 as I slowed for the light. When the engine was warm, the ICE would not be spinning, and I would be at 99.9 mpg.

If it happens for more than a few minutes after it starts, I would worry. But it sounds like normal operation to me.

[swiftyprius]

<div class='quotetop'>QUOTE(Slartibartfast @ Nov 23 2007, 09:26 PM) [snapback]543433[/snapback]</div>

That's what I have found. If the coolant temp is not up to the optimal level, the ICE still wants to spin for a while no matter how much the battery is charged. The time it runs seems to correlate with how warm the coolant likely is. I don't have a scangauge or anything, but generally I've found two stages. It always runs about 10 seconds after startup for about 1-2 minutes no matter what. If I sit in Park and watch the energy monitor, it will charge the batteries for a while, then the tone of the ICE will change and will stop charging the batteries. If I put it in gear during this time, the ICE will shut down but start back up above 7-8 mph for another period of time no matter if I otherwise would be coasting or gliding.
[/b]

Hasn't happened again, but the odd thing was it kept trying to stop, then started up again.

[tank_3]

<div class='quotetop'>QUOTE(swiftyprius @ Nov 13 2007, 05:57 PM) [snapback]539196[/snapback]</div>

Hi, This morning my two week old Prius did something weird. I rolled backwards out of the driveway, then went into drive, heading for the school bus, outside temp is about 68. After about 1.5 miles, went down a pretty steep hill, bringing the battery to green SOC, get stuck at the stoplight at the bottom.

I had the fan running just above low, no AC, and turn it off because of the stinky car in front of me. At this point I realize ICE is running for some reason, but then it starts to cut out, but then it kicks back in, and keeps cycling until the light goes green, about a minute. Has not happened again today.

Any ideas what this could mean?
[/b]

I have experienced the same "problem". My work is on a hill. Quite a few times when I left work and rolled down the hill, the battery was brought to green SOC, and at the stoplight at the bottom of the hill my ICE kicked in, cut out and then kicked back in, and kept cycling for about a minute. I did not have AC or even fan on. It is weird.

[patsparks]

I don't believe it's a problem at all. Just let the HSD do its thing, in unusual situations it will sometimes act unusually. If it's normal when the situation is normal it's just character.

[qbee42]

<div class='quotetop'>QUOTE(tank_3 @ Nov 28 2007, 02:14 AM) [snapback]545116[/snapback]</div>

I have experienced the same "problem". My work is on a hill. Quite a few times when I left work and rolled down the hill, the battery was brought to green SOC, and at the stoplight at the bottom of the hill my ICE kicked in, cut out and then kicked back in, and kept cycling for about a minute. I did not have AC or even fan on. It is weird.
[/b]

It's not a problem. I explained it once in this thread, but here it goes again: When the SOC becomes too high, the Prius will spin the ICE without gas just to burn off the extra charge. You typically see this at the bottom of a long hill, when you come to a stop. The ICE will be off, then come on and race, then go off, then come on and race again. The cycle continues until the SOC is at an acceptable level. The engine is not really running, it's just being used as a load to waste energy.

Tom