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SUVs Toyota RAV4 Toyota RAV4 Throttle Lag
79 messages, Last post on Aug 11, 2009 at 7:38 PM
You are in the Toyota RAV4 Forum. Your Hosts are steve_ & tidester
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Replying to: jimd4 (Aug 20, 2006 4:22 pm) |
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try adjusting your foot position on the accelerator, specially if you tend to be more of a toe tip driver. i.e. move your heel closer to the pedal so more of your foot is in contact with the accelerator. some people in other forums report this has helped reduce the lag they experience. it's been a theory of mine and a few others that there is excessive slop or play (mechanical compliance) in the pedal assembly, and possibly it needs to be replaced... however, no one has had that done that i know of, and it is conjecture. there are many theories about there being a transmission problem, a programming problem, shift solenoid problem, throttle body problem. it's really hard for anyone to know. that said, one owner of another toyota model (can't remember if camry or avalon) modified their pedal to make it stiffer in some manner and reported an immediate improvement, but later, his problem returned. that coupled with the foot placement reports does seem to point to the accelerator assembly as a potential root cause. anyway, give the foot placement a try and see if it helps. good luck. |
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Replying to: user777 (Aug 20, 2006 10:30 pm) To me, that would most likely point to something unique those few drivers are doing, quite possibly, probably, exacerbated by a so-far hidden (deadlock/deadly-embrace) flaw within the engine/transaxle's ECU firmware. The issue of foot placement, to me, provided something of a clue. Back in the fifties we knew, learned, that automatics would upshift more quickly with a slight momentary lift of the accelerator pedal. It has also become pretty clear to me that almost all modern day vehicles have automatic transmission control firmware designed to extend FE via adoption of certain techniques put forward in an engineering white paper published by Sierra Research late in the last century. Foremost among those was something referred to as ASL, Aggressive Shift Logic. The basic idea was to upshift the transmission at every possibility and thereby reduce the engine RPM to extend FE. There were at least two others, one of them being the use of the torque lockup clutch in lower gears to reduce "slush pump" losses provided the engine wasn't under heavy load. The shop/technical/repair manual for my 2001 AWD RX300 clearly indicates the above two features are in use. My 2001 911/996 Porsche C4 has DBW, but a manual gearbox. Since it's predominantly RWD, and with a definite rear weight bias, I can use engine braking quite safely if I wish, even on a somewhat slippery surface. So, how do you "treat" your accelerator pedal when you simply want to coast down to a lower speed, maybe even come to a full stop, VERSUS how do you treat it when you anticipate a need, during coastdown, to quickly accelerate? In my case in the 911 I might downshift and then leave the clutch engaged (until almost stopped) but lift the throttle in either case. Were I driving a FWD and the roadbed a tad slippery I would no doubt disengage the clutch should I have one available. On the other hand were I anticipating a need to "soon" accelerate I would disengage the clutch while leaving the transmission in the most appropriate gear for the upcoming acceleration. The firmware designers at Toyota?lexus have a rather difficult task. The firmware must be designed to upshift the transmission at every opportunity, a 9.8% improvement in FE is not to be sneezed at. And not being able to forecast and with no method to detect a somewhat slippery roadbed except after the fact, their design bias will not allow them to allow a downshift except on explicit and "certain" commands from the driver. As User777 has said, higher foot placement on the accelerator pedal does seem to have had a positive effect. Posters trying this have said they have encountered fewer instances of delay/hesitation via using this method. Higher foot placement would mean needing more foot pressure for a give distance and shorter travel distance for a given throttle opening. It would also mean, very likely, QUICKER release of the accelerator pedal, and coupled with the shorter distance involved this might just be the rear clue we're after. I have no doubt, absolutely NONE, that the firmware is written to detect the difference in the release RATE, and/or partially released position of the accelerator pedal in order to determine the correct action to take with regards transaxle activity, shift up, down or remain in the current gear ratio. A quick, definitive, FULL release of the accelerator pedal would undoubtedly indicate a wish to coast down to a lower speed. Whereas a partial release, or a "slow" release, possibly even toward a full release, might be interpreted as a desire to enter cruise mode, in which case an upshift would result. So, the priorities become... 1. Upshift for "cruising" whenever possible, feasible, for best FE. 2. Upshift on the slightest indication of "coast down" to best prevent loss of control from engine compression braking's interference with ABS on the front wheels. 3. Downshift ONLY with definite, definitive, action by the driver, action such that there can be no question but that the driver wishes to accelerate. See, the "deck" is stacked against you, quite firmly against you. But try the following. Do not "feather" the accelerator pedal in these instances, be a highly definitive "on/off" type of person/driver.
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Replying to: wwest (Aug 21, 2006 10:45 am) Do not "feather" the accelerator pedal in these instances, be a highly definitive "on/off" type of person/driver. you should only have to lift the foot off the accelerator pedal when applying the brake. if that doesn't work in these cars, it's game over.
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Replying to: user777 (Aug 21, 2006 1:22 pm) And I'm not saying you must remove your foot entirely from the accelerator pedal.....or maybe... I am.... With a DBW accelerator pedal now with a light duty return spring, can we really tell that leaving our foot "resting" on the accelerator pedal isn't having the same type of effect as those that are clearly, unconsciously, applying pressure to the brake pedal? More and more I am beginning to think a heavier accelerator pedal return spring, or a "torque motor" might be the solution. |
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for: FR Doc 05-1433 interesting reading. |
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NHTSA Consumer Complaint sent 22AUG06: There is a problem in acceleration delay/throttle lag in the 2006 Toyota RAV4. After taking delivery JAN06 and while driving 11K miles, I have experienced erratic acceleration problems. From complete stops or rolling starts, when turning corners in either direction, on uphill grades, or attempted passing, there is a significant delay in delivering forward speed regardless of what pressure is applied to the accelerator. After the delay, forward speed is delivered unexpectedly, causing the car to lurch forward suddenly. The forward speed lags continuously up hills, depending on the grade. Under these conditions, everyday driving is hazardous. I have experienced several close calls. The Toyota dealer dismissed initial complaints, stating that this was 'normal', and I put up with this for too long before insisting the vehicle be checked out. The dealer said no error codes were generated and no TSBs had been issued, and that they would have to duplicate the problem in order to fix it - as though we were the only people with this complaint. After some persistence, they gave the impression that they're well aware of a problem, but seem to be stonewalling while laying the blame on Toyota to issue a fix. This is a very dangerous fault. My online research has now proven very educational and has revealed that there are numerous complaints of this same problem on various forum websites. For Toyota dealers to pretend this is an isolated, insignificant problem is, at the very least, deceptive and may prove to be criminal, since this acceleration problem could easily lead to an accident. Note: I feel User777's treatise on the intricacies of the footfeed, while appreciated and interesting, has no bearing on this problem. I've driven most everything since the mid-60s with no problems adjusting to the vagaries of each vehicle, but this car is just impossible.
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Replying to: fordm (Aug 24, 2006 10:56 am) I suspect that were the brakes applied when you enter a coastdown period (release the accelerator pedal partially or even fully) the transaxle would not upshift as it does otherwise. I know this is asking you to adapt your driving style to what we all consider a serious flaw in these vehicles but you might want to try it temporarily just as an experiment.
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Replying to: wwest (Aug 24, 2006 2:30 pm) steve_, "Auto101: How To and How it Works!" #246, 24 Aug 2006 11:09 am |
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Replying to: fordm (Aug 24, 2006 10:56 am) if the accelerator pedal assembly with its position sensors or the throttle body valve with its position sensors and actuator had an issue with compliance, or calibration or "zeroing", what you are experiencing is exactly the sort of thing you should experience under the circumstances. unfortunately, it is speculation. noone has proved or disproved it, but one person got close my physically modifying his accelerator pedal. hmmm. i have proposed a means to acquire some objective information to prove my assertion, but noone has followed up on it unfortunately. i sense your frustration (apologies if i've increased it in any way) and further that you are making a meta-point or two: your foot placement and how you apply pressure is not helping the condition at all - it's simply not a matter of the car "training" you up on how to drive it ala you getting used to how it works. fundamentally, it doesn't work right. if so i agree 100%. everything is not normal with your car. the dealership has seemingly come to admitting as much. ask your dealership's head mechanic if it could be a problem with compliance or slop or a non-linearity in the throttle body position sensor or actuator, or sticktion, or same in the accelerator pedal mechanicals or position sensors. good luck.
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