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Toyota Sienna Hesitation

johnsiennajohnsienna Member Posts: 2
in Toyota
I just bought 2008 Toyota Sienna on February and experienced the hesitation when I tried to accelerate my vehicle after slowing down at the intersection at the speed between 5 to 10 mph. When I stepped on the gas at the speed I mentioned above, the engine seemed to roar up, but my car didn't move, and for a few second later it took off. It is intermittent. I had it serviced at the dealer I bought it from, but did not find any thing wrong. And I've been told by a few people including a service manager at the dealer that it is normal. They kept telling me that the new Toyota Siennas are computerized connecting the gas pad to the fuel injection. Because the signal has to move from the pad to the computer and to the fuel injection, that why a few second delay occured. I'm not a mechanic, but I know enough to understand how the computer works. Yes, there is a delay between touching the keyboard and printing data on the monitor. But as a users or the drivers, the delay should not be noticable. The service manager told me the specialist from Toyota come to dealer once a month and will have them checked my 08 Sienna. I also reported this issue to Toyota customer support. They documented the problem on my car and will set up to have my car checked at the dealer. It've been almost a month already, I have never heard any thing from them.

I just want to know if there are any 08 Toyota Sienna owners out there have experienced the same problem as I do.
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    wwestwwest Member Posts: 10,706
    Causative factors goes all the way back to '97, flawed transaxle design for the new RX300.

    Search/Google for:

    wwest dbw hesitation abolition
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    ateixeiraateixeira Member Posts: 72,587
    Here is my conspiracy theory on this matter:

    http://townhall-talk.edmunds.com/direct/view/.f169148/7

    That's just my opinion, though. ;)
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    johnsiennajohnsienna Member Posts: 2
    Is there any fix for this kind of problem?
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    wwestwwest Member Posts: 10,706
    Some of the Toyota and Lexus FWD & F/AWD '08 models have a new firmware feature that tries to judge the driver's intent by watching the rate at which the gas pedal is released. Fast and quick equals a wish to slow and therefore the transaxle will remain in a lower gear, slow and easy and it will upshift.

    My guess is that if the '08 owner/driver's can learn to adapt to this new feature the firmware "fix" might be made backwards compatible.

    The best answer is probably the one that Ford has chosen for the Edge, a variable displacement ATF pump, but that, most definitely, would not be backwards compatible.
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    lmo2lmo2 Member Posts: 1
    I have a 2008 Sienna Limited, bought in march. After about a month the check engine light and VSC light came on, I went to toyota twice . they told me it was because the gas cap was not put on correctly. Then I was pulling into a parking space and the van jumped foward and smashed into a parking pole. I brought it in and they told me the axel was not secured and I had leaked out all my transmission fluid!! They fixed it, supposedly, but now I constantly feel that hesitation. I am so frustrated and after reading many of these notes I am scared to drive it. We have been on the phone with toyota for a week and they are ..."looking into it". Has anyone had their toyota replaced because of these issues?
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    arodoryarodory Member Posts: 10
    I have a similar problem with the hesitation except I do not hear the engine race nothing happens during the hesitation delay...then it suddenly goes. They said the computer may need to be reset. Yours sounds like a transmission issue I have with my Honda. Did they resolve it yet?
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    arodoryarodory Member Posts: 10
    My 05 Sienna hesitates usually when accelerating after coming out of a turn. Originally, they said the computer may need to be reset. Later, dealer said they did not find a problem but now it is getting worse. Any advice?
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    arodoryarodory Member Posts: 10
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    ateixeiraateixeira Member Posts: 72,587
    Roll in to the throttle gradually. I think a large part of the delay is the trans hesitating before shifting down.
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    wwestwwest Member Posts: 10,706
    According to info at techinfo.toyota.com even the latest 2010 RX350 still has the 1-2 second "re-acceleration" downshift delay/hesitation. But the 2010 RX350 has new control firmware that attempts to alleviate the problem by watching the driver's actions on the gas pedal and thereby predicting, attempting to predict, the driver's next move/action.

    Assume you are accelerating even ever so slightly and accoringly the transaxle is in a lower gear ratio that it would otherwise be at your current roadspeed.

    If you now lift the throttle SLOWLY the system will predict that you wish to simply begin cruising along and the trnasaxle will shift into the highest gear appropreate to the current roadspeed.

    On the other hand if you lift the gas pedal FAST/QUICKLY the assumption will be that you wish to slow, perhaps using a bit of engine compression braking, and the transaxle will be more likely to remain in the current "lower" gear ratio.

    In this latter case, FAST/QUICK release of the gas pedal, and you NOW wish to quickly return to acceleration, there is no gear upshift pending, in process, nor having just completed. So the transaxle is fully "armed"/prepared for even a downshift if that is what is required for the level of acceleration your "new", re-acceleration, gas pedal position dictates.

    In about 1998 Toyota/Lexus commited to a major (as it turns out more MAJOR then they predicted) transaxle design change mostly in favor of improved FE. The design change resulted in their transaxle's INABILITY to support two gear changes in quick succession in some situations, mostly if the gas pedal has been released into a position that results in an idling engine or almost so.
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    wwestwwest Member Posts: 10,706
    No, the delay is the result of either a pending upshift, an upshift in process, or an upshift just having been completed within the past few hundred milliseconds. In that situation the transaxle simply CANNOT support a downshift and so DBW is used to delay the rise in engine torque. The engine torque cannot be allowed to rise until (presumption of engine at/near idle) the ATF gear type oil pump can (re-)pressurize enough ATF to support the next gear change.

    To reduce weight, complexity and improve FE the "old" line pressure accumulator was eliminated back in about '98 in order to allow "real-time" control of ATF line pressure. This was primarily the result of the need to provide the extra space needed build more robustness into the Camry transaxle now that it had to serve duty in the upcoming HEAVIER RX300.

    But without the accumulator to sustain line pressure the line pressure collapses to near zero with each gear change if/when the engine is idling or nearly so.

    Ford has adopted the same ATF "real-time" line pressure control but also adopted a variable displacement ATF oil pump so line pressure recovery can be quick(er) even with the engine idling. That variability also allows them to improve FE to an even greater extend via reducing the pump displacement volume as engine RPM rises.

    Ford has a better idea.......sometimes.
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    arodoryarodory Member Posts: 10
    Thanks- it started recently and got worst... does that sound right to you?
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    ateixeiraateixeira Member Posts: 72,587
    Thanks for the detailed write-up.

    Most people just look at the number of ratios in an automatic.

    I keep telling them the 4EAT in our 2009 Forester is a whole lot more responsive than the 5 speed auto in our Sienna but noone wants to believe me.

    I sense that when I go over a speed bump, I let off the gas slowly, it shifts to 4th I think, then I'm back on the gas and it takes an eternity to figure out it should be back in 2nd, 3rd tops.

    So basically the Sienna seeks the tallest gear possible to improve FE but cannot conduct multiple shifts back-to-back without a slight delay between each one.

    Sound about right?
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    wwestwwest Member Posts: 10,706
    Not quite. The problem only arises when the engine is near or at idle and the ATF pressure is being, or has just, "just", been exhausted due to a throttle lift upshift. "Ask" for a downshift for acceleration in the above circumstance and for up to 2 seconds you are left "hanging".

    Just as in your "speed bump" example.
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    kenjomariscakenjomarisca Member Posts: 1
    i had the same problem for years,including "pinging"when accelerating out of a turn,toyota said i was not using the proper gas octane and that if it's not chevron that usually happens,so i started using only chevron 91 octane but the problem was still there.take note that 2004 and later siennas does not require 91 octane,this is one point to argue with toyta,but anyway there is a recall to adjust the computer settings to correct the engine pinging problem and transmission hesitation problem and siennas are supposed to be covered up to 95,000 miles if i'm not mistaken,search google for toyota "TSB"or toyota service bulletins.i took mine back to dealership and had them reset the computer,now mine accelerates very good and i dont notice the hesitation.
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    atherather Member Posts: 3
    I have the same problem with my 2005 XLE.
    So can it be fixed then? Is there a TSB for this?
    Thanks
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    hewhohesitateshewhohesitates Member Posts: 2
    Hi John, I first read your post in the spring of 2009 because I was experiencing exactly the same thing with my 2008 Toyota Sienna. The hesitation in shifting at low speeds when accelerating after slowing down to turn a corner occurs intermittently but is quite noticeable. I've been back to the dealer several times, have been in touch with Toyota Canada - (last contact was in May 2009 and still waiting for a cAll back - it's October!). There is a culture of denial around this problem that is unbelievably arrogant. I'm very disappointed with the lack of commitment to customer satisfaction. My advice to anyone looking at the Sienna is ... buy a Honda Odyssey. I sure wish I had.

    John - If you - or anyone - are still following this thread, I'd like to hear how your situation is. Thanks.
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    yatesjoyatesjo Member Posts: 186
    The hesitation coming off of corners is a design issue with the transmission (if it were Microsoft they'd call it a 'feature'). Every Sienna has it and it is not a defective part so the dealer cannot do anything for you. Toyota may re-engineer it in some future model, but don't expect to get the upgrade.

    I can reproduce it every time I want to in my van with a hard brake followed by heavy throttle so the behavior cannot even be called intermittent. It is however, very driving style dependent- in my normal driving pattern I rarely see it My advice: brake further back, gently and with an even deceleration in anticipation of the stop so the down shift doesn't occur so close to when you want to hit the gas and the problem will go away (as a bonus your passengers will be more comfortable since they won't be jerked around as much.)
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    ateixeiraateixeira Member Posts: 72,587
    I agree and here's how I explained it:

    http://townhall-talk.edmunds.com/direct/view/.f169148/7#MSG7
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    usa09usa09 Member Posts: 1
    You and "johnsienna" give a very accurate description of the transmission hesitation. This is definitely a problem with the 08. I also owned an 04 Sienna and did not have this problem. This hesitation has become much more noticeable after we reached 20-25k miles. It is intermittent but very noticeable.
    The dealer said they can not do anything unless there is a TSB. I am adjusting my driving to anticipate when to lighten the foot on the throttle. Hopefully a bigger transmission issue will not develop in the future. I have been happy with the Toyota Sienna otherwise. How this 08 transmission continues to operate and the service provided by Toyota will determine if we stay a Toyota owner in the future.
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    buzz19buzz19 Member Posts: 1
    This problem just continues to carry on from one model year to the next. My 2009 Sienna is experiencing the same type of hesitations that are previously mentioned. I took it into a Toyota dealer last summer and they claimed they never experienced this hesitation on the test drive but they did a "reset" anyway and suggested that I make sure I keep changing my air filter at appropriate times. They refused to go on a test drive with me. I got the sense that they were aware of this type of problem but chose to ignore it like Toyota Canada prefers to do with this issue.
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    wwestwwest Member Posts: 10,706
    Toyota is VERY well aware of the transaxle downshift delay/hesitation problem.
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    yatesjoyatesjo Member Posts: 186
    If you've read this thread and understand the issue is not regarded as a fixable problem for the dealer why waste your time taking it in for service? I mean if you know every single van has this issue, they can't fix it and adjustment of driving patterns alleviate it and that all the dealer will do is look at it, test drive it, reset it and give it back to you almost exactly as you brought it to them why waste your time?
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    wwestwwest Member Posts: 10,706
    But it is a "fixable" problem, how and when remains the question so drilling down at the dealer on regular, otherwise free time, basis might well be worthwhile.
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    yatesjoyatesjo Member Posts: 186
    If you have free time to spend sitting around at a dealer your time is a lot cheaper than mine. More power to you all- I couldn't do it.
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    frizzy1frizzy1 Member Posts: 1
    Shortly after we bought our 2004 Sienna van XLE AWD, I experienced this hesitation issue incessantly. I solved it by starting out in 3rd gear, moving to 4th for around town, and drive for faster speeds. It works beautifully though some who are with me don't understand.
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    hank0821hank0821 Member Posts: 1

    I have a 2008 Toyota Sienna that hesitates approx 1 out of 3 times after stopping at a stop sign and then trying to accelerate again. It is a 1 to 2 sec delay. I can hear the rpms rising but there is not an immediate response from the transmission. I have brought this to the dealerships attention and they sat that they can't duplicate the problem.. My response at this point is Yeah.. Right!!!

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    tappantobytappantoby Member Posts: 1

    2012 CAMRY LE has hesitation problem. Been to a dealer two times. Fix lasted 1-2 weeks
    write to your BBB or state attorney general and advise them...FYI AG Eric Holder just filed a law suit against Toyoto for the carpet /pedal acceleration problems. I feel this may be the next law suit against Toyota. THEY DO NOT HAVE A FIX FOR THIS SERIOUS HESITATION / ACCELERATION PROBLEM,OTHERWISE IT WOULD NOT BE HESITATING.

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    giffordpagiffordpa Member Posts: 1
    I had a 2012 Toyota Tacoma that did this same thing. I just read this thread today while researching something else. I couldn't take the hesitation any longer, I also thought something major was wrong, and traded it in on a 2015 RAV4 last week. The RAV4 doesn't have the hesitation at all.
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