1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Push Gas Pedal and NO GO!

Discussion in 'Gen 2 Prius Technical Discussion' started by animalcontrol, May 28, 2008.

  1. animalcontrol

    animalcontrol If my mouth moves, ignore me!

    Joined:
    Jan 7, 2008
    68
    0
    3
    Location:
    Greenwood, IN
    Vehicle:
    2008 Prius
    As much as I don't think my "technical" jargon can communicate this problem effectively, I doubt that I'm the only person to have expireneced this so I will try and explain.
    Backround
    I have an 08 Touring Prius that I've owned since mid-Jan. Currently 9800 miles (I commute 100 miles/day 90% hwy) and this happened this morning on my morning commute. I'm averaging 50.0 mpg lifetime and about 55 since weather warmed up. This morning was about 50 F and this incident happened about 25 miles into my commute (car was plenty warmed up)
    I have a 3-4 miles stretch where I cut through a town and the speed limit is 30 mph (I glide or electric 95% of this). At the end of town, I merge (ramp) back onto a state hwy and the new speed limit is 45.
    Problem
    As I merged onto the hwy, I was still electric only (30 mph). When I saw my opening, I pressed the gas pedal approx. 1/2 way to accelerate to 45 and ease into the opening. The car just stuttered, a fast repeated stutter! The ICE didn't come on. No acceleration just thunk, thunk, thunk, thunk for about 4 seconds (I had my foot still pressing the gas pedal). I released the gas pedal, the car went into regen mode and I pressed the pedal again. The ICE started normally and I accelerated up to the speed limit (the drivers behind me were none to happy). The rest of my commute was normal.

    Was this an exception? Does this happen on occasion and therefore might be "normal"? I went to college for mechanical engineering and I have good handle on the ICE but admittedly accept that I don't know enough about the hybrid system to "know" about this.
     
  2. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,073
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    It's not normal. What is normal is a slight hesitation while MG1 spins up to start the ICE. You normally feel the slight hesitation when moving under electric only, and then suddenly ask for a lot more power, such as merging. MG1 is spinning to keep the ICE from turning when it suddenly gets tasked with starting the ICE. To do this it has to dramatically change its speed, perhaps even change direction. That takes a small but finite amount of time, so it feels like a power cut-out or hesitation.

    I'm wondering if your half-power request was hovering on some sort of a threshold, causing the ICE to come in and out. I would have expected enough hysteresis in the control loop to keep that from happening, but it is possible. If you feel that again, try giving it more gas and see what happens.

    It's also possible that you are having engine trouble. While very reliable, a misbehaving ICE could produce the symptoms you describe.

    Tom
     
  3. seasalsa

    seasalsa Active Member

    Joined:
    Feb 29, 2004
    1,278
    20
    0
    Location:
    Kent, WA
    Vehicle:
    2010 Prius
    Model:
    II
    You did not mention weather or road conditions! I notice you has some rain last night. I would guess that when you accelerated there was either oil film or water on the road surface and the traction control kicked in.
     
  4. animalcontrol

    animalcontrol If my mouth moves, ignore me!

    Joined:
    Jan 7, 2008
    68
    0
    3
    Location:
    Greenwood, IN
    Vehicle:
    2008 Prius
    No, I very familiar with this hesitation. This was very pronounced.

    [/quote]I'm wondering if your half-power request was hovering on some sort of a threshold, causing the ICE to come in and out. I would have expected enough hysteresis in the control loop to keep that from happening, but it is possible. If you feel that again, try giving it more gas and see what happens.[/quote]
    Good suggestion. If it happens again (I hope not), I will try more gas.

    [/quote]It's also possible that you are having engine trouble. While very reliable, a misbehaving ICE could produce the symptoms you describe.

    Tom[/quote]
    I would expect some "idiot" lights to have shown up or stayed on and I had none.

    Thanks for your response.
     
  5. animalcontrol

    animalcontrol If my mouth moves, ignore me!

    Joined:
    Jan 7, 2008
    68
    0
    3
    Location:
    Greenwood, IN
    Vehicle:
    2008 Prius
    No, road was dry but the idea of the traction control is interesting. I have never had the traction control kick on before so it is possible. Is there a better description of how that feels?
     
  6. qbee42

    qbee42 My other car is a boat

    Joined:
    Mar 2, 2006
    18,058
    3,073
    7
    Location:
    Northern Michigan
    Vehicle:
    2006 Prius
    Invoking traction control causes a sudden loss of power, followed by application of power. If there is still a traction issue, the cycle will repeat until it clears up. At low speeds it will make a sound like "roomph, roomph, roomph..." as the wheels power up and slow down cyclically. The yellow traction light on the dash illuminates when traction control is active.

    That could be what happened with you. At the speeds you were traveling, it would feel like a stuttering loss of power, which is consistent with your description. Did you go over any bumps or loose stones?

    Tom
     
  7. animalcontrol

    animalcontrol If my mouth moves, ignore me!

    Joined:
    Jan 7, 2008
    68
    0
    3
    Location:
    Greenwood, IN
    Vehicle:
    2008 Prius
    I didn't notice any loose stones but this time of year, every shoulder of the roads here are covered in sand put down from winter.
    It sounds very plausible that my traction control engaged. I managed to get through the winter without it but I used it in the spring!
     
  8. richard schumacher

    richard schumacher shortbus driver

    Joined:
    Mar 27, 2004
    7,663
    1,037
    0
    Location:
    United States
    Vehicle:
    2004 Prius
    Model:
    N/A
    Yep, sand on the road will do it.