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Toyota/Lexus transaxle shift delay



  • user777user777 Member Posts: 3,341
    can't we capture that if indeed another sub-system is asking for attention?

    back in '02 when this problem first started to be noticed, or get documented by owners, did they have VSC and/or Trac?

    if it were interplay with other systems, i would think it would affect more vehicles, but i understand a yaw or other direction accelerometer, or steering wheel input sensor, or wheel slip indication could be different from car to car and cause a subsystem to make more requests for attention than others.

    still, we have to walk before we run. i want to see the timeline of brakes applied, shifting, throttle demand and command, yada yada in a timeline.

    ideally, i'd like to see the data from two vehicles, one with the issue and one without, driven by the same person. i know this is asking for a mountain, so i'll be satisfied with a teeny tiny hill to help everyone get calibrated.

    who else is good for $25? what's the hesitation folks? ;)
  • bettersafebettersafe Member Posts: 92
    As in any survey, the development of the questions on the survey are vital. For example, at one time I seemed to think that cars purchased in Canada might have different computer firmware logic than cars purchased in USA. I have seen one comment about folks who place their foot on the gas when they start their car (which can confuse the "zero" setting of the DBW system). Another set of comments on folks who place their foot on the brake when they start their car... Other comments about two-foot drivers, one on the gas and one on the brake.

    With all the "smarts" built into these cars, it is very hard to tell which set of behavior/conditions may be most correlated with the undesired transmission behavior.

    If someone had a public web site where possible clues could be posted. . . this might be helpful.

  • bettersafebettersafe Member Posts: 92
    I do not own a problamatic car, but I will throw in $25, for the good of those who suffer the symptoms.
  • scoti1scoti1 Member Posts: 676
    By questionnaire, are you thinking of a list of questions we could ask those experiencing hesitation?
  • bettersafebettersafe Member Posts: 92
    Yep. . . .
  • shepalishepali Member Posts: 72
    Sorry, can't try that - I'm not driving the car any more - drives me too crazy.

    But...I do not think this would help, based on my previous experiences. The actual symptoms initially started when approaching a stop sign or stop light, not coming to a complete stop, then pulling away. In my case, this was almost always in a straight ahead situation. I supposed its possible that I would have moved the wheel - so who knows!

    After time, the symptoms increased in frequency and in severity such that it began to happen in parking lot/garage maneuvers (which would obviously involve more steering wheel movement). Then, after time, I started to experience overall shift pattern problems at other unpredictable times. I now even sometimes experience jerky shifting when on the freeway, in both up and down shift situations. But like I've said before, it is very unpredictable and inconsistent.
  • shepalishepali Member Posts: 72
    It seems interesting to me that you (and others?) often refer to the RX330 model as having these issues. Because I have also driven at least 3 of those - and never had a problem. Where, in contrast, every ES330 I have driven has exhibited the symptoms (again, at least 3).

    Do any of you know any differences between the two vehicles that would result in me (the supposed cause of these symptoms in my car - according to Lexus) not having the issue in both models? Maybe exploring that would also help to figure out whats going on?

    On a side note, when the local dealer was originally trying to work with me on this - they told me that I would have this problem in any ES, thus getting me a new ES would not solve the problem. They told me my 'driving style' was not compatible with that car - they quoted 3% of the population as having this problem with that car. However, they did suggest the RX, GS, and IS as possible replacement vehicles for me. I specifically asked how they can be so sure that I wouldn't experience the same thing in those cars and the GM explained each of those three models separately to me, and the difference in the transmissions. Unfortunately, I don't recall what they said though :(
  • wwestwwest Member Posts: 10,706
    2004 RX330 electrical wiring diagram Pub. No. EWD563U page 177.

    "4. Mutual System Control

    To efficiently operate the VSC system at its optimal level, the VSC system and other control systems are mutually controlled while the VSC system is being operated.

    Engine Throttle control.
    The engine power does not interfere with the VSC brake control by controlling the opening of the throttle and reducing the engine output.

    Engine control and electronically controlled transmission control.
    The strong braking force does not interfere with the braking force control of the VSC system by turning off the accel. and reducing changes in the driving torque at shift-down."

    (End quote)

    As one can readily see from the above statements the inadvertent operation of the VSC system can result in engine dethrottling and delayed downshifts.

    If the VSC detects over-stearing it will apply, modulate, the brakes on the outer turning wheels. The greater the degree of over-stearing the harder that outer front wheel will be braked.

    On the detection of under-stearing it will apply both rear brakes (RX330 only??) while controlling engine power.


    "The engine power does not interfere with the VSC brake control by controlling the opening of the throttle and reducing the engine output."

    Take notice that this statement does not necessarily mean that engine power is reduced to idle. It may mean that engine power is "set" to match road speed, no acceleration torque nor any compression braking.

    "The strong braking force does not interfere with the braking force of the VSC system by turning off the accel...."

    ...turning off the accel....

    I take it this means opening the firmware control loop between the gas pedal (accelerator) and the throttle valve.

    Therefore I take this to mean, again, that the engine throttle control is taken over by VSC to prevent any significant level of engine compression braking.

    "...and reducing changes in the driving torque at shift-down..."

    Wouldn't this mean delaying down-shifts until the VSC ceases operation?

    Since for most of the vehicles exhibiting the hesitation/delay the "outer turning wheel" is also one of the two driven wheels, or as a minimum for AWD one of the two primary drive wheels it is no surprise.

    I think we already know that the VSC system firmware has a proactive mode wherein it dethrottles the engine to alleviate the potential for rollovers in an accelerating and/or tight turn.

    So, what might make it, the VSC system, think it needs to "operate" just before coming to a full stop or just as you decide to downshift for acceleration.

    An unequal rotation rate at the driven, front, wheels versus the rear, that's what!

    Would those of you experiencing this problem please, if you don't mind, check and be sure all of your tires are equally inflated. Maybe even a pound or two extra in the front since the majority of the weight is there?

    Remember that if you adjust the pressure you will need to "normalize" the new tire pressure levels.
  • shepalishepali Member Posts: 72
    tedescm1 - I am one of the people experiencing the symptoms, and yet I agree with scoti1 here. It really is a very nice car - and I really do like it. I just can't stand the way it reacts to my driving style. So, if your driving style isn't one that is incompatible with the car - you may be very happy with it.

    When scoti1 says "an extra long test drive", I recommend trying to keep the car overnight, and driving it on YOUR roads, in YOUR traffic, with YOUR normal driving style. Throughout this process I have realized that I drive differently when someone is in the car (even my husband), and when people are in the car it doesn't react as severely as when I am alone.

    So, take that for what its worth - and make you're own decision.
  • shepalishepali Member Posts: 72
    Sorry to blow your theory - but I have used premium fuel since I purchased the vehicle. I recently switched to regular - based on someone's post. The symptoms either got worse, or stayed the same - can't be sure. But bottom line is that I used premium fuel for the first 10k or so miles, and I have the problem worse than most people. So, unfortunately, I don't think the fuel has anything to do with the underlying issues.

    Having said that - the dealer did ask me if I used premium during one of our conversations. When I said yes, they didn't continue that line of thinking. So, they must think it CAN improve performance for some.... but that's just my impression.
  • shepalishepali Member Posts: 72
    you had posted this info from Sierra before, and every time I read it I think - THAT IS IT!!! That is exactly what I'm experiencing.

    Wonder why Lexus can't apply some type of software/hardware change that overrides all of that - JUST for those that experience the negative symptoms like I do? Or, the 'override button' some of us have suggested - like a sport mode, or something, whereby the user of the car accepts that their gas mileage will be affected, but their performance would be improved.
  • lmacmillmacmil Member Posts: 1,758
    Just found this forum. Anyhoo, my wife drives a 2004 Highlander with 3.3L/5 sp and I drive an 05 Camry SE-V6 with same drivetrain. I think her engine is rated at a slightly higher torque output which leads me to believe the engine management software is slightly different.

    The downshifts in my Camry definitely come quicker and with less throttle input than the HL. In fact, had I never driven her HL, I wouldn't be aware of the issue based on my Camry. Even with the HL, I have only experienced a very noticeable delay (approaching 1 second) on a handful of occasions.

    I think wwest's speculation on the old hesitation forum that the issue is somehow related to throttle management seems very believable. That would explain the variation in the perceived problem.

    It would be really interesting if someone who felt they had a severe problem could trade cars with someone who felt they didn't. That would tell us something about the effect of driving style on the issue.
  • shepalishepali Member Posts: 72
    Well, I AM experiencing the symptoms, and I actually enjoy surveys/questionnaires (odd, I know!). So, if you guys want to ask me questions, I'd be happy to respond. As for what you posed herein:

    For example, the questionnaire might indicate that folks who use Gasohol are more likely the have the problem than folks who do not burn gasohol. Folks who burn premium may have less problems.
    What's gasohol? I just use either Premium, or Regular gas, depending on the prices and my pain threshold. See my previous post about my gasoline buying habits.

    People who have replaced their transmission fluid in the past "X" miles may not have the problem. How many people have checked their transmission fluid level when trany was cold. How many people have checked trany level when hot.
    I rely on the dealer for all of these things. I take my car to the dealer every 5k miles, as suggested by the manufacturer.

    People that start their car and let their car warm up for 60 seconds with no pressure on the gas pedal might have fewer problems.
    Definitely don't do this, at least not on purpose. I back out of my garage right after I start the car, then I do sit there for a few seconds as the door goes down and I set my destination in the Navigation system.

    Drivers with a lot of stop and go driving may have the problem more than those with constant driving speed.
    Yes, I experience the problem more in stop-and-go traffic, and yes, I do drive in more traffic than I do at a constant driving speed.

    A person who drives very lightly on the gas might have more problems than a heavy footed driver.
    I would generally call myself a heavy footed driver - but I guess it really depends on what you mean by that. I made a previous post (can't recall if it was this forum or the other) discussing how I am frustrated by the lack of responsiveness in the gas pedal - i.e. when you let off of it (partially or completely), the car does not quickly decelerate. So this results in me switching from the gas pedal to the brake much more frequently then I do in other cars I drive. Based on what I've read here, I think that may be contributing to the symptoms, but I don't know how to change that given how the car reacts....

    And, in case you didn't see my previous post - I am not a two footed driver.
  • wwestwwest Member Posts: 10,706
    1. As I said above, be sure your tire pressure is the same all around.

    2. Have the dealer service department follow the "by the book" procedures to calibrate the stearing wheel position sensor and the yaw rate sensor.

    If either of these sensors are out of calibration then the VSC will, may be, "hair-triggered". If so it will activate at the slightest indication that the vehicle is not following the correct line of travel, and that may very well result in delayed downshifting and dethrottling.
  • shepalishepali Member Posts: 72
    Well, I'm torn by the idea. Generally speaking, I like survey's and experiments. And, I've actually thought about offering myself up to Lexus as part of my negotiations/arbitration - it occurred to me that maybe the reason they haven't found a solution is that none of their engineers experience the symptoms as severely as someone like me. So, if they had a guinea pig to try out their software/hardware fixes on - maybe that would be helpful. But then I think that they must not be interested in that - or they would have already found someone like me over the past 5 model years.

    As for your suggestion - I just ask myself what I would get out of it in the end, in return for the time and frustration. I'm a very busy person (which is why my posts only show up every two weeks or so....), and to take the time to do that just doesn't rate high enough on my list of priorities. I'd rather be out riding my Harley, or on the lake! And, I'd rather Lexus just take my car back - and we can just agree that my driving style is incompatible with their car.

    Having said all of that - I think I do meet your requirements. I do experience the problem - quite severely, I might add! I have a laptop, and I am computer savvy enough to figure out most software. Depending on how this software works, I may not have a CLUE what the output means though - I presume that's where you engineering geeks come in (sorry - no offense!!).

    It just comes down to the time and energy factor. Describe that to me more....
  • tkevinc1tkevinc1 Member Posts: 30
    I want to insert a little twist to this discussion. I have a 2006 Avalon touring and I have the transmission "hesitation" for a lack of a better term. The twist is the car will go for days and drive like a dream. No transmission issues, no engine knock - just a wonderful vehicle to own. Then for inexplicable reasons it will go for a week or more where it cannot find the right gear to save its butt, the engine knocks like a diesel and just has all kinds of issues that are certainly related to the engine and system management controls. No-it is not the gas I am using and I am not a left foot braker **but I do admittedly go WOT frequently**. Regardless, the difference in the car from time to time is truly astonishing. I am a very analytical person and I spent 2500 miles trying to track the when and where of the issues and never found any like conditions that brought this about. The only thing I can tell you is that a LONG drive on the interstate seems to improve the conditions from time to time. That makes me think it is the "learning capability" of the system. How do you even present this to a dealer? All but one issue are central to the pleasure of driving the car only. The other is a hazard. On more than several occasions the transmission has failed to attempt a gear change altogether. When accelerating from 45-55 mph (passing situation) the tach just went to redline and nothing happened. I had to let completely off the throttle, allow the rpms to return to idle, and go again to get any action at all. I am at a loss for solving these issues but I wonder if my intermittent problem doesn't negate some of the possibility of driving style and the like as the culprit.
  • shepalishepali Member Posts: 72
    With regard to trading cars with someone - I haven't had the opportunity to do exactly that. But, as I've mentioned in previous posts, I have experienced the symptoms in EVERY ES330 I have driven. These were dealer loaner cars - both 05 and 06 model years. At least 3, maybe ever 4 total.

    So, it seems to me that, in a roundabout way, I did do the experiment you suggested. And, its supported by the dealer acknowledging that I will experience the symptoms in any ES, and even stating it is due to my driving style.

    So, it does in fact appear to be a driving style issue that is incompatible with the software/hardware of the vehicle.
  • wwestwwest Member Posts: 10,706
    experiencing the problem happens to be driving a 2004 RX330 and wants to try an experiment I can give you instructions for disconnecting the CAN (Controller Area Network) unique to the stearing wheel position sensor and the yaw sensor from the system.
  • shepalishepali Member Posts: 72
    Well, my Lexus ES330 can also be bipolar like this (although I have never experienced the red lining you described). And I too am an analytical person and have tried to figure it out. Based on my own experiences, I actually think the intermittent problem actual supports the driving style as the culprit. I agree that driving a long, consistent speed drive on the interstate will improve the learned memory of the system - until it is replaced with a new learned memory. According to the dealer, this takes about a week of normal driving to re-learn the memory.

    The only correlation I've been able to find - and I'm curious if you reflect and notice the same thing - is that the reaction of the car is impacted by my state of mind, stress level, mood, etc. The more stressed I am, and thus the more 'agressive' I drive, the worse the car gets. Then, with normal, relaxed driving, it will settle down again. This is not an immediate reaction - again, it takes a while for the ECU to over-ride previously learned habits.

    I use the word 'stress' loosely here - its like when I've had a bad day, or am really late, or get pissed off by something another driver did. I take all of those things out on my driving style. Weave in and out of traffic more, tailgate more, floor it more, etc.

    By chance, tkevinc1, can you draw a similar parallel, when you reflect on your bipolar car?

    P.S. As I type all of this, it makes me wonder - am I the bipolar one???? hehe! :blush:
  • bettersafebettersafe Member Posts: 92
    WWEST: I love reading your theories. . . This is as good as any murder mystery ! As a systems engineer, working as a automation programmer, I fully understand how a high priority safety sensor like VSC could take precedence over other engine management functions. We should add VSC onto the questionnaire list. I do not think that all Avalons have VSC. That might help explain some differences.

    Of all the forum entries that I have read, some claim that individual cars have bad traits. . . . and these cars probably have individual problems: such as sensors out of calibration or barely within calibration. All instrumentation has reporting accuracy and tolerances. Some cars may be operating on the outer edge of the acceptable tolerance. For example, some cars were reported to be delivered low on transmission oil, but not low enough to be reported as a problem.

    Other forum entries claim that a particular driver can make any car of a type exhibit poor performance. . . which indicate that driving style is a factor in transmission performance. Note: driving style is "a" factor, and not "the only" factor.

    When you get both a car operating on the edge -and- a driver with the aggravating driving style, I think you end up with one really unhappy owner. I feel for these guys/gals. You spend megabucks on a car and get something that you are uncomfortable to drive. Not a good thing.

    There are so many variables: Oxygenated fuels, anti-knock sensors, fuel mass sensors, etc, etc. My head spins.

    There has to be some automotive school out there with all the OBD hardware and software who could use this as a class project. What a great learning project for the technicians! To be a student of WWEST's theories must be worth several thousand dollars of education.

  • shepalishepali Member Posts: 72
    One thing to add - although maybe not meaningful, since it can't be proven - the dealer told me that they tested every single possible calibration there is in my car, and that everything was 'normal'.
  • hylynerhylyner Member Posts: 216
    Bettersafe, you are to be commended for suggesting a more structured approach to discussions about this hesitation isue.
    It looks to me that your approach has resonated, at least for some.
    Like you, I'm equally impressed with many of the technical analyses produced by Wwest. They will be very helpful in the end to be sure, and they have played a part in helping others understand how DBW systems work.
    As you have observed, the more that's learned about these systems though, more combinations and permutations arise, and the picture becomes an increasingly complex mosaic of possibilities. The only practical way to unpack that murder mystery is to find as many clues as possible, and do it in a logical and organized manner.
    I believe getting as much detail as possible from those who have experienced the issue is critical to finding answers.
    Simply cutpasting repetitive tales of woe into the mix doesn't really help much. It's like the old addage--if you're lost in the forest without a map and compass, you're likely going to spend a lot of time looking at trees. Simply complaining about being lost is a waste of time.
    Here's some information (call it "clues") regarding our new Highlander--V6 with 4WD. Currently at 1800 miles.
    It drives smoothly with no hesitation, lurching, searching for shift points, etc., for all intents and purposes all the time.
    However, I've spent the equivalent of about 5 hours trying to simulate some of the conditions reported by others.
    I have had some success in getting it to respond similarly--albeit it took an awful lot of trial and error attempts to get it to do so.
    Condition No. 1--a short delay and somewhat firm shift from first to second. Nothing serious, but noticeably different from a normal accelleration, ie, not as smooth. Here's how I did it. Accelleration with very light (really light!!) throttle application, up to about 12-1300 rpm, maintain a steady (very light) throttle application, then the tranny will sort of pause and shift slowly, and engage 2nd gear more firmly than normal. This is repeatable--but don't do it in traffic because all the cars behind you are PO'd because of the slowness in getting moving. Bottom line, it's not a condition that one would do in an even remotely normal situation.
    Condition No 2. Driving along at 40-50 MPH (15-1800RPM), hammer it to WOT for a moment, release the accelerator completely for a moment, go to WOT again, release throttle once more, then hammer it back to WOT and hold it there. The tranny seems to drop right out of gear, then reengage in a much lower gear-not sure but I would say around 2nd or maybe 3rd. Accelleration comes after a moment of hesitation--less than a second--with a really firm initial push--almost like the vehicle has been thrust forward from behind.The engine ramps up to max RPM instantly. It will almost snap one's head back when the tranny engages. From then on it accellerates normally to about 5000+ RPM or so while upshifting back up thru the gears to 5th without a problem. The vehicle doesn't do this if I hit WOT and hold it down--it downshifts smoothly but firmly, then accellerates normally in a lower gear back up to 5th. PS--I strongly recommend not trying this experiment at at home--or when the State Police are about!!
    Condition No. 3. At about 25 MPH, gently push the throttle down very, VERY lightly--not much happens until the throttle is depressed a bit further then the vehicle accellerates normally. It seems to just want to sit at the same throttle setting for a moment until the tranny is satisfied you intend to speed up. Again, not really a normal situation.
    No. 1 Son has an older (05) HL. Next time he visits I'll take it for a drive and see if I can get it to do the same.
    He's just as curious as I am about this debate, although he doesn't have any complaints about the vehicle, and doesn't have any interest in looking for or talking about problems. Wise kid--He says He's got more important issues to worry about than problems he doesn't have.
  • scoti1scoti1 Member Posts: 676
    It wasn't really my theory. People have been told by Toyota and Lexus to switch to premium to alleviate the problem. I think even wwest has suggested it could help. I thought it would be good to put it to bed. However, after looking up those other posts it seems like it could provide *some* improvement for *some* vehicles so it could be worth a switch from regular to premium if you want to see if it will lessen the severity of the symptoms. You don't seem to be one of those that it is going to help. Maybe because your problems are so severe.
  • wwestwwest Member Posts: 10,706
    IMMHO most, or a clear majority, of the complaints of engine/transaxle downshift delay/hesitation in various forums all over the internet seem to involve only the FWD or front biased AWD versions of the Toyota and Lexus 5-speed vehicles.

    The shop manuals tell us that if the VSC activates it assumes control of the throttle and the transaxle shifting sequence. The VSC only activates, really, if it detects over-stearing or understearing. When it detects under-stearing, "plowing", it applies the brakes to both rear wheels (at least for the RX300,330), on the assumption that slowing the vehicle even slightly might allow the front wheels to regain enough traction to alleviate the condition. For over-stearing it modulates the braking of the outer turning wheel according to the severity of the level of over-stearing.

    As one can then see, the result of VSC activation and assumption of the throttle and transmission shift sequence might be entirely different for a FWD drive versus a RWD vehicle.


    When a RWD vehicle is understearing some level of engine compression braking at the rear, DRIVEN, wheels might even be desireable. Whereas on a FWD in an under-stearing situation engine compression braking on the wheels already having lost traction would be highly undesireable. Obviously allowing a downshift on a FWD vehicle during this situation might even lead to total loss of control.


    To correct and help recover from over-stearing the brakes are applied to the front outside wheel. If the driver happens to be braking during the incident the VSC will actually release some level of braking at the inside front wheel.

    The VSC activation will likely prevent all engine compression braking or even acceleration torque by modulating the throttle to match engine RPM to road speed. Obviously any impending downshifts would be delayed until the situation has passed.

    So, for me, there is now enough information available to conclude that for whatever reason the VSC is activating, just ever so briefly, and causing these incidents of engine/transaxle shift delays.

    Under-stearing, plowing, is much more common on a FWD vehicle, while over-stearing is more common on RWD vehicles, often the result of a too heavy throttle application.

    So which driver is most likely to notice, let alone complain, about inadvertent and brief VSC activation and the resulting loss of throttle control and delayed downshifts?

    And keep in mine that as you drive around that corner the front wheels are turning at a different rate than the rear and the outside wheels are turning faster that those on the inside of the turn. So if the VSC is somehow faulty (lack of sensor calibration or tire inflation disparity) and always on the "cusp" of activation accelerating around that turn would certainly trigger VSC.
  • tkevinc1tkevinc1 Member Posts: 30
    Your description of "aggressive" is basically the way I drive 99% of the time. I am not sure that it causes the issue since I can drive for some time like that with the car performing like a sports car. Maybe I am one of the drivers that causes some of this discussion but I have owned three cars previously with electronically controlled transmissions, drove in the same manner and never had an issue. On top of that I have an engine knock that comes and goes with the transmission issue that sounds like valve train noise probably from the VVTi. It just seems like the management systems are at fault.
  • wwestwwest Member Posts: 10,706
    Any level of engine knock/ping, any level at all, would certainly exacerbate the engine/transaxle downshift delay. That's why the dealers are recommending a switch to premium fuels to help alleviate these instances. Likely also why switching out the MAF/IAT module helped in at least one instance.

    A replacement MAF/IAT module, just by happenstance, might have resulted in an overall richer mixture.
  • lmacmillmacmil Member Posts: 1,758
    You mean, of course, oversteer and understeer ;)
  • wwestwwest Member Posts: 10,706
    Isn't "steer" beef on the hoof?
  • bettersafebettersafe Member Posts: 92
    Someone on this forum must have a contact with one of the automotive teaching schools which teach Toyota diagnostics. And several on this forum have cars that misbehave. Can't we put the two together? The automotive school must have all the necessary OBD hardware and software plus a bunch of bright-eyed students to make use of the ODB tools. Seems to me that one day with a misbehaving car and a skilled ODB user, and we would have some answers. Some of the theories of WWest would be disproven, and some of them would be supported. Given this evidence, WWest could refine the theories into more concrete suggestions for resolving the problems.
  • user777user777 Member Posts: 3,341
    well written. i'm at a loss to understand at this point why we are the only two willing to put up some $$$ to fund the experiment equipment, but also why someone with the issue isn't begging to be the "subject" of the experiment. ;)

    i mean their car being the subject.
  • wwestwwest Member Posts: 10,706
    Does everyone experiencing, for certain, the engine/transaxle delay/hesitation have VSC??
  • lmacmillmacmil Member Posts: 1,758
    My Highlander and Camry both have VSC but the downshift delay on the '04 HL is definitely more noticeable than on the '05 Camry.
  • bettersafebettersafe Member Posts: 92
    I believe owners of misbehaving vehicles are frustrated that Toyota or Lexus dealers have not done the research to resolve the problem. The dealers must have the OBD equipment and training. . . so why don't they spend a day to test WWest theories? At one time I followed this discussion as a potential Avalon buyer. Now I follow the discussion simply as a curious engineer/programmer. I have nothing personal invested in the outcome.

    For owners who have misbehaving vehicles, and have been told that "nothing is wrong with the car" or "the problem is the driver". . . And some have heard this from multiple dealers. . . . I can understand their position. They want an answer to be developed for them by Toyota / Lexus.
  • wwestwwest Member Posts: 10,706
    Dealer "service"....

    They didn't even have a clue as to how to check the VC, viscous clutch/coupling in my 2001 AWD RX300...
  • wwestwwest Member Posts: 10,706
    [quote name='jragosta' post='179883' date='Feb 13 2006, 10:16 PM']
    [quote name='wwest' post='179643' date='Feb 11 2006, 06:01 PM']
    A CLUE......

    IMMHO most, or a clear majority, of the complaints of engine/transaxle downshift delay/hesitation in various forums all over the internet seem to involve only the FWD or front biased AWD versions of the Toyota and Lexus 5-speed vehicles.


    That wouldn't possibly be related to the fact that the majority of cars on the market today (especially Toyotas) are FWD?

    True, but....

    Toyota, having adopted the fuel saving features recommended back in 99 by Sierra Research, would have applied it across the product line, Toyota, Lexus, FWD, RWD, AWD and 4WD. I haven't been able to find even one complaint for the nature of the problem as described in the TSB in any Toyota Vehicle other than those with FWD or front biased AWD.

    And keep in mind that when VSC is active it assumes control of the throttle valve and the transaxle to prevent or delay downshifting. The two complaints common to the hesitation symptom are delayed downshifts and engine acceleration delay.

    Let's for the moment assume that the VSC system falsely thinks the vehicle is under-stearing/plowing. Remember that under-stearing/plowing most commonly occurs on FWD vehicles when the front tires' roadbed traction coefficient is too low for the combined forces, lateral (directional control) and braking or acceleration.

    Obviously there would be two versions of the VSC firmware, one for FWD and one for RWD.

    Since under-stearing is so highly unlikely in a front engine RWD vehicle might it be totally ignored?

    But even if not totally ignored how high might the triggering "moment" be set?

    But under-stearing on a FWD vehicle is highly likely, much more likely.

    If the vehicle is under-stearing/plowing, not following the direction "set" by the front wheels, how do you control/adjust the vehicle dynamically to devote the absolute maximum front tire roadbed traction to lateral control? You neutralize the engine drive/lag torque by assuming control of the throttle and matching engine RPM to roadspeed based on the current gear ratio, and obviously you cannot allow any pending downshifts. In the case of my 2001 RX300 it actually applies the brakes to both rear wheels on the assumption that whatever roadbed traction might be remaining at the rear can be used to slow the vehicle and thereby help regain traction at the front.


    Rare event for FWD, VERY rare event!

    And remember that with a RWD vehicle in over-stear one very likely still has the entire level of front tire roadbed traction to devote to directional control/recovery.

    Looking back on my 50 years of driving I cannot think of even one instance wherein an unintentional or inadvertent skid, over-stearing, wasn't the result of too much engine torque at rear end. I can only think of one instance wherein my lifting of the gas pedal and/or releasing the clutch didn't quickly result in a skid recovery. That one instance was the result of inadvertently and unknowingly have cruise control engaged (below my actual road speed of the time) on an ice and snow covered roadbed.


    Rare event in a RWD vehicle but common to FWD.

    I can only think of one time and that was in the rear engined 78 Porsche 911. My 2001 AWD RX300 has threatened to under-stear a few times but that was quickly overcome by VSC activation in each instance.

    So, were it YOU designing the VSC firmware for Toyota wouldn't you make the FWD version "hair-triggered" as pertains to under-steering? And the RWD firmware "hair-triggered" for over-steering"?

    And just mighten that "hair-triggering" cause exactly the hesitation symptom drivers of FWD or front biased AWD are reporting?

    Might you even have a "pre-emptive" firmware routine to help alleviate top heavy SUV rollovers?

    How would you do that?

    Prevent the driver from accelerating into/through a tight turn...

    No high engine torque production and/or not downshifts to apply additional torque for acceleration.
  • bettersafebettersafe Member Posts: 92
    A key point would be if the hesitation symptoms happened only in a curve where the steering wheel in off-center -or- if the symptoms happen equally often when the car is pointed in a straight line.
  • wwestwwest Member Posts: 10,706
    Neither the stearing, nor the stearing wheel, are necessarily off-center when the stearing wheel position sensor is off-center, miscalibrated.
  • lmacmillmacmil Member Posts: 1,758
    You are obviously a very smart guy. Please tell me you know how to spell steering as in steering wheel. There is no such word as stear.
  • bettersafebettersafe Member Posts: 92
    We all have our quirks. The spelling of English is so illogical, that I can understand how a logical person as WWest might have difficulty with it !

    As per the steering sensor being out of alignment. . . this is a very interesting possibility... It would explain why some cars are very tempermental if their programmming believes that they are in a turn all the time. I doubt that a dealer would check the calibration of this sensor while looking for a transmission shifting quirk.
  • user777user777 Member Posts: 3,341
    maybe. isn't stability control supposed to flash a light or ding a chime when it's engaged? so, your just talking about one sensor telling the system be prepared but not the whole system engaging, or part of the system engaging like retarding the throttle?

    a bit confused.

    ok, how about a yaw rate sensor that is flawed...

    what does changing lanes and slowing to make a turn to the left from the center lane have in common?

    allright, how is stability control disabled again?

    happy valentines day to everyone endulging us.
  • wwestwwest Member Posts: 10,706
    I think back in about the 5th grade (53?) at Primos elementary in Secane PA. I was taught to differentiate the two this way. Yes, I noticed that "stear" is not in the online dictionary but look up stearing committee.

    If VSC can activate to a level that I can "feel" via my butt sensor and yet not be quick enough to see the indicator then I'm sure it can activate (100 milliseconds??) for a short enough period that the buzzer doesn't sound.

    And of course if this is due to a VSC firmware bug, which is highly likely IMMHO, anything is possible.
  • user777user777 Member Posts: 3,341
    to test the theory, one disables VSC, right? can this be done safely (caveat: this road closed for test purposes, do not try this at home)?
  • wwestwwest Member Posts: 10,706
    The schematic shows an ECU module connection for a "Trac off" switch with a note indicating the actual switch is only provided for 2WD vehicles. Don't know if the AWD firmware would resond to the switch nor if it did would "trac off" apply to VSC functions.

    I would imagine that removing the ABS pumpmotor fuse as I did on our Jeep during the summer months would result in deactivating all of these functions, VSC/Trac/BA/EBD/etc.

    But unlike the Jeep in which only ABS was being disabled I wouldn't advise doing this for other than a brief test or getting unstuck via intentional wheelspin.
  • scoti1scoti1 Member Posts: 676
    If you were in grammar school when I was (the 60's), I would have to ask you, "what were your teacher's smoking?". You steer a car, the male bovine is a steer, it is a steering committee. I wouldn't steer you wrong.

    That aside, we all make spelling mistakes at some time or other, I just don't see it as a big deal on a message board unless I can't understand what you are trying to convey and that was not a problem in your posts.
  • wwestwwest Member Posts: 10,706
    Google for:


    Last word from me on the subject.

    Other than a "steer" isn't exactly a "male" bovine.
  • scoti1scoti1 Member Posts: 676
    Dang, wwest, you are stubborn. Here is my last word. I googled for "stear" and got mostly links to someone's last name. A couple used stear as you do, but they seem to be typo's on someone's homepage. I even searched a British dictionary on your behalf, and still no such word as "stear". And Merriam-Webster's on-line dictionary defines the noun, steer, as: 1 : a male bovine animal castrated before sexual maturity.

    I found one dictionary with the following definitions:

    stear-var. of stearo- before a vowel: stearate.

    stear(o)- (stear(o)-) [Gr. stear, gen. steatos fat] combining forms denoting relationship to fat.

    STEAR stands for Strategic Technologies in Automation and Robotics

    Back to the stearing/steering discussions :)
  • wwestwwest Member Posts: 10,706
    Google for:


    100,000 plus hits.


    "stearing wheel"

    23,000 hits.
  • scoti1scoti1 Member Posts: 676
    Well, you got me on that one. But it appears in no dictionary (except the medical definition and acronym in my earlier post for "stear") so all I can say is that there are at least 100,000 occurrences on the internet where someone has misspelled steering as you did. You have a lot of company.
  • bettersafebettersafe Member Posts: 92
    I saw a post on the AVALON 2005+ forum where an owner can turn VSC off. [ The procedure is amazingly non-obvious.] This would allow an errant vehicle to be tested with and without VSC.
  • bettersafebettersafe Member Posts: 92
    In fact, the procedure to turn off VSC is so obscure, that I wonder if it is a joke ???
This discussion has been closed.