transmission slips when car is parked outside and the temperature is hot

Discussion in 'Gen 2 Prius Main Forum' started by Jonesie12a, Aug 6, 2009.

  1. Jonesie12a

    Jonesie12a Junior Member

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    I am not sure whether I am having a transaxle issue, battery issue, or inverter issue... When I get into my car at the end of the day after it has sat outside in the heat I experience a condition where the car hesistates to go when the accelerator is pressed. There is a one to two second pause from the time that I press the accelerator pedal to the time that the car actually starts moving. If I move my foot on the accelerator pedal any at all, the car jerks and hesistates as if the transaxle is slipping. It does not act the same way as if the SOC of the battery was low. The battery charge goes from what ever it was when I first parked it down to one bar. Once that happens I get no regen braking. I thought that it was the A/C load that I was putting on the system, so I raised the temp up to 85 and that had no effect. Tried driving with the windows down to let out the heat but that has had no effect either. The engine runs constantly (which is expected due to the heat and the battery SOC). When the temp is lower (in the mornings) I do not have this issue. I do hear the battery fan running. My main concern is the way that the car behaves when accelerating or even crusing. I am concerned that if someone else drives the car (my wife) that they will not know that the car hesitates and get into an accident. I don't think this issue is normal, even due to the heat as there are alot of Priuses around here. Anyone else experience this issue or have any suggestions? The inverter pump failed early this summer and was replaced so I am thinking it could be that rather than a transaxle issue. Vehicle is MY 2004 with 78k miles. Mileage has taken a nose dive this summer to the upper 30's, FWIW.
     
  2. Jonesie12a

    Jonesie12a Junior Member

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    I should also mention that I have had no CEL or warning lights regarding this.
     
  3. justlurkin

    justlurkin Señor Member

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    I remember reading a post last year when someone was having issues similar to yours... Turns out the battery vent was clogged up with a lot of debris. Cleaning out the debris from the battery vent solved the problem. Worth checking out. Good luck.
     
  4. Jonesie12a

    Jonesie12a Junior Member

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    I went out and took a look at the battery vent. No dust or fur that I can see. I found the post that you talked about and in it was instructions on how to remove the inside cover from the back seat. Looked pretty clean. I very rarely carry anyone in the back seat and I have no pets to dump hair in the system.
     
  5. JimboK

    JimboK One owner, low mileage

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    First, fuel economy in the upper 30s in the midst of an Arizona summer doesn't surprise me if your driving is mostly at non-highway speeds. The AC really pulls fuel economy down at low speeds; it forces the ICE (internal combustion engine) to run considerably more than it would otherwise.

    Second, the transmission has nothing to "slip" (I'm not dismissing your symptoms). There is no changing of gears in the Prius' continuously variable transmission.

    One of the first things to come to mind is "hot battery." When the battery and the rest of the hybrid system reach a certain high temperature, the car takes steps to reduce battery use (using it heats it more). The battery fan runs, as you've observed. Because the electric motor is doing less work, its normally-available immediate torque is reduced and the ICE, with less instantaneous torque, is doing more of the work. I can see how what seems like the sensation of a slipping transmission can be felt in those conditions.

    What I'm puzzled about is this:

    So this happens only with high SOC? And how do you know you have no regenerative braking? That is quite abnormal if that is indeed true. Are you seeing green arrows on the Energy monitor during braking or coasting? That indicates regeneration.

    As for SOC quickly dropping, I have seen that on first startup on a hot day while running AC. In the first minute or so of warmup the car uses the battery preferentially anyway (in all temperatures) as ICE heat is diverted to warm the catalytic converter. Then the AC will be running its hardest to cool a very hot cabin. On hot summer days with the AC on, especially (again) in slow traffic, I've seen SOC drop very quickly after a day-long sun-baking.

    Even in the Mid-Atlantic, I go to great pains to try to park in the shade in the summer. I also have tinted windows, a windshield sunshade, and I keep my windows cracked. The battery is a large thermal mass and it cools slowly. Prevention is the best medicine.

    I'll be interested in hearing from others in AZ or similar climates to get their take on this.
     
  6. northwichita

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    The battery charge goes from what ever it was when I first parked it down to one bar.

    Not during the park, when you first drive it right? Either way I would investigate the HV battery, sounds to me its on its last legs. My battery charge only goes down like that when in EV mode,driving several blocks, without the gas engine running. I'm unsure on your next step, but also wanted to point out about the comment
    remove the inside cover from the back seat. Looked pretty clean.
    I drive in dusty conditions, so occasionally use an air chuck with an air compressor to blow out dust that settles inside the vents, you could try this in case there is something blocking air flow you can't see. I would guess though it would take awhile for a clogged system to cause the problems you have.
     
  7. Jonesie12a

    Jonesie12a Junior Member

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    This happens at all of the SOC's, and the battery eventually drops to 1 bar and remains there. I know that it is not regen braking as it shows engine power to the wheels as I am braking all the way to the point I have stopped. No green bars/arrows at all. It almost seems as if the engine is pushing the car at a stop as I notice that I have to apply a bit more brake pedal force than usual.

    What I meant by not acting the same as if the SOC was low means that when this is not happening and the battery level drops to 2 bars or lower, the issue is not the same. The car is sluggish when that happens, but the issue that I am experiencing is best described as a "slip". I guess it could better be described as it seeming like the transmission is switching between electric and non-electric modes when there is any change to the accelerator pedal while the engine is revving very high if there is any acceleration. When I accelerate normally, the engine revs to its highest point and is very slow to drop RPM's when I let off. I made sure I was not in B mode as well.

    I know that the battery is hot. I am concerned about the jerking in the transmission as a side effect... whether it is something bad. I am pretty sure that this couldn't be a widespread problem as there is a definite driveability issue when this occurs. I wish that I had a covered place to park, but I don't.

    This isn't a standard A/C draining the battery issue, as I have turned off the A/C and drove with the windows down and this still happens with no change from when I drive with the A/C on.
     
  8. Spartane

    Spartane Member

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    The gasoline engine and the motor/generator are mechanically geared together. The gears push against each other and the difference between the two is fed through the driveshaft and moves the car forward.

    So if the gasoline engine is revving without the car moving forward, then it means that the motor/generator is freewheeling (little or no power being fed into it and little or no power being taken out of it).

    You've been getting poor mileage for a while now and the battery fan is always running. This suggests to me that the HV battery is damaged (there's likely a few cells internally shorted) and the charging system is going into overdrive trying unsuccessfully to bring it up to full charge. This constant charging is both lowering your mileage and causing your battery to overheat, damaging it still further.

    So I'm guessing that the HV battery problem has now progressed to the point where it is going intermittently open when it gets hot, causing the motor/generator to freewheel and the gasoline engine to rev, since it has nothing to push against.

    I'm also guessing that with a new HV battery your mileage will return to normal.
     
  9. 2009Prius

    2009Prius A Wimpy DIYer

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  10. georockc

    georockc Junior Member

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    I was just getting on to write a similar post, as it sounds like I had the same thing happen to me today (and about 3-4 times over the past). This has only happened to me in the summer (again a hot Arizona summer) after the car has been sitting at work. It usually starts and gets going just fine. I've noticed it as I've been leaving the lot (slight uphill after slowing for a speedbump). I'll place my foot on the accelerator and it feels like the car lags. It feels like nothing is happening. and today I noticed that my SOC had dropped to only one bar, and the engine ran all the way home. There was regenerative braking (according to the MFD).

    I should add that I could hear that the battery fan was running at the time.
     
  11. richard schumacher

    richard schumacher shortbus driver

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    It didn't do this in past summers, right? Take it to a dealer. Something in the traction battery system is too hot and from this distance we can only guess why.
     
  12. Jonesie12a

    Jonesie12a Junior Member

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    I will. Just curious as if someone had any issue like this. Since I am getting no CEL's or red triangles I am hoping that the dealer won't just pass me off.
     
  13. Jonesie12a

    Jonesie12a Junior Member

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    No, the motor revs anytime I accelerate, whether it be from a standstill or trying to increase speed while moving. When I move my foot in the least little bit either accelerating or slowing down, the car jerks and shudders, but when accelerating it goes to full RPM as if I had the pedal to the floor.

    I plan to stop by the dealer and see what they think. If the battery was an issue, I would have hoped that I would have gotten a red triangle by now.
     
  14. Jonesie12a

    Jonesie12a Junior Member

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    Have you ever had any shuddering in the transmission or a really long hesitation when taking off from a stop when this happens? (longer than when the battery SOC is in the 2 bar range)
     
  15. torrens89

    torrens89 New Member

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    Hi Jonesie12a:
    Hopefully this one year belated reply finds that your problem has been solved. My 06 Prius had a bad HV battery at 'only' 43000 miles. The dash warning lights all lit up with the red triangle very large. This was in January here near Boston, but in the 20's.
    I don't understand why your dash warning triangle did not come on. Perhaps your battery was more marginal than mine.
    I phoned the dealer early next morning and had AAA flatbed the car to the dealer. By early afternoon their super Prius tech had pronounced the HV as bad. Toyota paid for a rental for the five days it took to ship a spare from somewhere on the east coast by truck. No air shipment allowed. Hmm?
    At the time of my battery trouble this was the first such failure in the Boston region. Notably, the HV battery is covered for a long time for cars with CA spec emissions. 10 yrs or 150k miles I believe.
    Re the 'brake' problem, I've been the guy who leaves more room between the car in front and me. Thus, I haven't had to slam on the brakes very often. I do notice the loss of power on right turns when accelerating from a stop due to traction control. Thus, I try to avoid that situation. Toyota tried to make the car feel like regular cars, but one does learn of the foibles of a high tech vehicle.
    I still like the car, but it takes a bit of learning how to live with it. Having had over a dozen cars in my time, the Prius is still the best overall. Now if I could only find better speakers for the JL 'premium' sound systems. ANYONE HAVE SOME SUGGESTIONS? The factory tweeters in the sail panels are definitely poor.
    torrens89
     
  16. kohnen

    kohnen Grumpy, Cranky Senior Member

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    Likely a non-issue.

    If the battery's really hot, the computer does what it can to:

    1) Cool it off (by running the fan).
    2) Not heat it up any more (by not trying to pull power out of it).

    This means that, from a stand-still, the computer requires ALL of the power to the wheels to come from the engine. In order to supply ALL the power, the engine has to operate at a higher power region of its RPM curve - it needs to spin quicker.

    This is just your computer taking care not to overheat the traction battery.
     
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