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Toyota/Lexus transaxle shift delay



  • wwestwwest Posts: 10,706
    Not the way equations work in my world. When trouble-shooting any problem the very first thing you do is remove, subtract out, any non-pertinent information.

    Do millions of drivers not have this problem?


    Does the TSB adequately address the problem for some?


    Does any of above tell us anything about the few that are still having the problem, some of those even having had the TSB applied?

    Not that I can tell....

    So, what parts of the "equation" do you think we should continue to address?

    IMMHO what's needed is to look into what anomalies exist, vehicular or personal, within the relatively small group still experiencing the problem.

    And having an accelerator pedal with a fully released voltage output that is always above 0.8 volts, up to 1.1 volts, purely by happenstance, might be the sole causative factor.

    That might make it look like the gas pedal is never fully released, always slightly depressed, as might someone who has a habit of left foot braking.

    Suppose, in these few cases, the engine/transaxle ECU "thinks" you are braking with your left foot when you're really not.

    What might the ECU do in the case of an actual left foot braker?

    It certainly would not, might not, allow the engine to develop any serious level of torque with the brake applied. But no, we know that isn't happening, too many people driving merrily down the road, cruising along, with the brake lights shining brightly.
  • Put an end to this ridiculous, contrived topic rather than encouraging any more discussion.
  • billranbillran Posts: 113
    Fair enough. Whether the points I mentioned are factored in or factored out, the result is the same. I would still have to wonder though. Without a car that consistently displays the phenomena to test the theories on, this discussion will just spin on for eternity with no practical result.

    Hey Grandaddy, what happened to that post you put here yesterday, I rather enjoyed that. And I think you hit close to the mark. You have to be careful how you word your posts though, sensitivities run high.
  • user777user777 Posts: 3,341
    well then now you are on to something man.

    it's possible the link i posted to ECU and TCM functionality, specifically TPS is older and relates to the 4-speed transmission era technology. the TPS was clearly a variable resistor, and the IDL sensor a physical switch. you're saying the newer systems use hall effect transducers? i have no reason to doubt you.

    look folks, we are at a disadvantage here not being Toyota Design Engineers with access to supplier information and details of the implementation.

    the puzzle WWEST is dealing with at the moment is how can a calibrated transducer (in this case the accelerator, not the throttle position sensor) have a return to zero value that is very discrepant from nominal and still usable by the control system?

    the problem people are reporting is comming off the accelerator (Throttle closed), then re-applying the throttle with a delayed response.

    this slop or non-linearity and how it may be treated in SW can very well be at root cause.

    like I said a few times before, someone with a really problematic car should be pushing to have first their TPS and Throttle Body replaced, and then their Accelerator Pedal assembly. this most recent post by WWEST might suggest the reverse order of replacement.

    in my opinion there *IS* more your service manager can do for you!
  • wwestwwest Posts: 10,706


    User777 and the Boeing 777 is the first with DBW...

    Any correlation?

    In any case the information in #239 above was taken directly from the 2004 Repair Manual for the RX330, Pub No. RM1027U1 Volume 1.

    Throttle Valve position sensing page 05-93 to 05-103
    Accelerator Pedal position sensing pages 05-249 to 05-261

    To continue....

    When I had my 2000 GS300 the engine surge at throttle tip-in (actually accelerator pedal tip-in, initial slight application/depression) would oftentimes result in wheelspin, especially on my gravel driveway at home. Even absent the wheelspin, on dry pavement, I was never able to learn to feather the gas pedal at tip-in lightly enough to avoid an initial acceleration surge consistently.

    I initially assumed the throttle linkage had too much backlash, too much slack in the mechanical connection from the gas pedal to the throttle valve. I adjusted out all of the cable slack I could but yet the problem persisted.

    So I went in to Lexus of Bellevue to explain the problem and see if there was a fix available. I gave up after the service manager spent so much time trying to convince me that my 2000 GS300 was DBW and therefore mechanical coupling slack/backlash could not possibly have been, be, the problem.

    Just how does the DBW system decide how or when the accelerator pedal is fully released? Obviously that is something it "learns" during that initial 15 second period after a new one is installed and the engine is started.

    If the "learned" voltage at that time is below the useable range, intentional, designed in "slack" then all is well. But what if, by sheer happenstance, a definite minority of accelerator pedal assemblies come from the factory with a fully released VPA sensor voltage above the explicit, 0.8 volts, "useable" voltage?

    Lets jump over to the throttle valve for just a moment. The throttle valve assembly comes from the factory with an explicit "throttle valve fully closed" VTA1 sensor voltage, 0.69 volts. 0.93 volts is the explicit VTA1 voltage for 6 degrees o throttle valve opening, likely the idle position.

    So the validity of the throttle valve fully closed signal can be readily checked, on the vehicle, in the field, embedded in the firmware, by simply driving the throttle valve servomotor toward the fully closed position. Basically trying to drive it beyond the fully closed position. If the resulting sensor output signal is something other than 0.69 volts (+/- and RCH) then the throttle valve assembly has malfunctioned.

    I can easily see how the accelerator pedal fully released position is "learned" during that 15 seconds even if it happens to be above the "useable" 0.8 voltage level. But what if another aspect of the engine/transaxle ECU firmware still thinks the higher voltage means the accelerator is still depressed, but only at certain specific times or unique driver actions?

    Page 05-250 has a chart showing, labelled, "Usable Range". The chart/graph indicates that the VPA usable range starts EXPLICITLY at 0.8 volts and ends at 3.55 volts plus or minus 0.95 volts. Obviously the VPA signal voltage can drop below 0.8 volts and as a designer that would be acceptable to me, even desirable to be sure I never opened the throttle valve when the gas pedal wasn't depressed.

    What doesn't make sense to me is the acceptable VPA output voltage tolerance level of 0.5 volts to 1.1 volts for a fully released accelerator pedal. That means that a fully released accelerator pedal's VPA sensor output voltage can be as high as 0.3 volts above the bottom end of the usable range and still function correctly.
  • user777user777 Posts: 3,341
    If you can regularly experience the hesitation when slowing, then getting on the gas with your vehicle, either in stop and go, getting on a ramp after applying the brake, or slowing in the median to prepare for a left turn while waiting for an opening in traffic, and getting on the gas, would you try this simple experiment?

    In the morning before you drive, put both feet firmly on the floor mat so as to not touch the brake or the accelerator pedal. Turn your ignition key to the "ON" position but resist the urge to turn it all the way to START. Wait about 10 or 15 seconds for the fuel pump to establish fuel pressure.

    Then with both feet still on the floor mat, turn the key to start, but do not give the vehicle any additional gas!

    Providing the car starts and keeps running (it should), wait an additional 20-30 seconds before putting your foot on the brake and taking it out of Park.

    Now, put the vehicle in gear and drive as you normally drive and try the scenario underwhich you typically experience the hesitation.

    Please report back your results (worse, better, no change) and the scenario where you experience (experienced) the hesitation:

    Also take note if your general shifting has changed if at all.

  • wwestwwest Posts: 10,706
    I went back and reviewed bkinblk's trial with disconnecting the battery each day. It appears that disconnecting the battery definitely helped alleviate the problem, at least in the short term.

    I think what this may mean is that the parameter causing, or contributing heavily to the problem, is not driver unique alone.
  • user777user777 Posts: 3,341
    disco on the battery probably wipes the mapping or learned driving behaviors in addition to other sensor data that has to be built up again over time. Thus the ECM/TCM may revert to defaults.
  • wwestwwest Posts: 10,706
    Driver charactoristics, unique or otherwise, are erased from ECU memory the instant you turn the ignition key off. Each time you start the vehicle in motion the ECU begins the "re-learning" process regarding driver charactoristics. Within 60 seconds you have been "binned" into one of four driving "styles". By the time 3 minutes have elapsed you have been further refined into 1 of 16 "styles". Thereafter the ECU(s) keep a running record of not more than the previous three minutes and will revise your style on the fly as it becomes necessary.

    The above is taken from an SAE white paper I found on the internet quite some time ago and I don't remember if it was unique to any specific marque or not.

    But I think you will agree that none of the driver unique "learned" memory aspects can be carried over to the "next" driver.

    Otherwise my wife might find driving our Lexus somewhat discomforting after my weeks of slinging it around curves again and again.
  • wwestwwest Posts: 10,706
    Okay, how do we know that there are not two "forms" of engine/transaxle delay/hesitation? One form which Toyota has deemed "normal", to protect the drive train, and a second, extended one, causing delays of one of two seconds are more.

    I can fully and easily accept Toyota' explanation that there is an intentional delay in allowing the engine to develop a substantial level of torque as the downshift is completing. I often drive a stick shift and I do not wish to be replacing the clutch prematurely. So I am careful to not apply gas inordinately quickly as I engage the clutch after a downshift.

    So I can fully accept Toyota explanation that the delay is to protect the drive train. But just how long a delay are they talking about? Certainly one that would be noticeable if one were in an especial hurry to accelerate.

    But clearly, that wouldn't be 1 to 2 seconds as is being complained about, a few hundred milliseconds, maybe.

    So, ALL of Toyota's electronically controlled transmissions with DBW are exhibiting some level of downshift delay. Enough of a delay that any driver having experience with previous, non-DBW transmissions, will definitely notice when quickly returning to acceleration circumstances.

    So, what if the anomalous "extended" delay only occurs on vehicles with Trac, or even VSC.

    Look at the contention between the parties, posters, involved, some say the delay is hazardous. In my opinion a 1 to 2 second unpredictable delay might very well put one into an unsafe condition. But many who claim to be experiencing the delay contend "no way" to the unsafe or hazard issue, and often further dispute the 1 or 2 second amount.

    Good, logical evidence that there may be two forms of the delay/hesitation.
  • hylynerhylyner Posts: 216
    The technophobes are starting to repeat themselves. It seems they're back where they've already been. That often happens when folks get lost in a maze with no road map, or when they ignore others offering assistance.
    They just go madly off in all directions--which is exactly what's happening here ---again!
    All kidding aside, several times already you guys were pointed to the accellerator pedal position interface as something to examine. A couple of times by someone who seemed to know a little about it (in the old hesitation forum) and then by yours truly when I cutpasted one of those earlier suggestions for you just recently.
    Every time the suggestions were either sluffed off as not relevant, or just ignored. Mostly ignored. Suddenly it's the latest greatest theory of all--for 5 minutes. Does that mean if it isn't your idea it's not worth a look?
    Or maybe if enough theories get tossed into the air, one of them is bound to land closer than the others?
    Well, I think (hope) you may have at least part of the puzzle in front of you again, even though it was right there all along. Don't be so eager to brush it off this time. Stick with it for more than 5 minutes, at least.
  • wwestwwest Posts: 10,706
    IMMHO the BIG mistake, horrible mistake, John Kerry made when the opposition was accusing him of flip-flopping was not standing up and saying:

    "yes, absolutely, I'm the worst (BEST?) flip-flopper there is. When I learn new information about some issue and it is timely to do so I re-think my position, and when and if it becomes appropriate I revise my position/opinion."

    Personally I have read over the information in the shop/repair manuals several times in the past, what, six months. But it was only day before yesterday that I noticed the anomaly between the VPA signal level tolerance and the fact that that tolerance might well put it outside of the factory documented operational parameters.

    Has Toyota missed that for all this time also?

    Maybe so.

    Maybe they have been looking at the wrong problem. The "normal" "protect the drive train" designed in engine/transaxle delay/hesitation, and not even realizing that there is a RARE ABNORMAL one.
  • user777user777 Posts: 3,341
    I agree WWEST is all over the place.

    I believe I was the one who suggested a long time ago a non-linearity with the accelerator pedal. ;)

    anyway, based on WWESTs recent post, I'm suggesting a very easy experiment to see if ignition/starter on calibration of the zero-demand for the pedal might be at play.

    don't label me please, and don't claim adding a "just kidding is sufficient". i work in a pretty technically rich domain and am no technophobe.

    and please, ADD something helpful rather than being critical of the posts. unless of course you're trying to get this thread shutdown like the other. you're doing a fine job.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 58,488
    The best way to keep things running smoothly around here is to remember the Golden Rule...don't personalize your comments..."attack ideas, not people"....if you find your fingers typing things like "your problem is that you are a _____", that's asking for a fight.

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  • I wonder if it is possible that some people get paid to post on this forum. If this is indeed possible, I then wonder how they are paid. It would be my opinion that they must be paid by the WORD and not by the number of posts. What a horrible way to earn your daily bread this would be.

    If this were the case it would account for any post you might see that just went on and on in circles, mindlessly repeating the same message over and over and over and....
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 58,488
    Well that's the very type of post that doesn't work!

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  • hylynerhylyner Posts: 216
    So I'll just respond to all:

    Mr. Shifright:

    One more try--no funny stuff this time. (I am now patently aware you guys have no sense of humor!!)

    Mr. Shiftright.
    Geez, I really was just trying to be lighthearted and at the same time get a message out. Honest!!
    Please accept a sincere apology.
    Sorry I PO'd you all--it wasn't supposed to be that way--I guess it came across wrong.

    For the record User777, I am as interested as anyone here in getting to the bottom of this mysterious hesitation issue!! Please, believe me.
    I am not trying to get the forum shut down!!! (That was kinda unfair of you to say that--almost like when you tagged me as a Toyota employee--but given your impression of my post, I guess I can't blame you for feeling that way. I really didn't know or think the word technophobe was derogatory)
    I have some info on your test idea if you aren't too incensed toward my input. Perhaps later?

    Guys, what I was trying to say was if you ever want to get to first base in this quest, you should really consider a more structured approach.
    Instead, you seem to be directionless--wandering all over.
    That was why the "Madly Off In All Directions" comment.

    Wwest--your theories are excellent. Your spontanious creativity is really impressive. There's a place for that. But please, try to stick to one thing for a little longer because bouncing a flood of ideas around tends to throw things off kilter. Be a little left brained for a change, and maybe there could be better progress here. I know it's your forum, and you're entitled to whatever you want, but there could be an end in sight if you give it an opportunity.

    Grandaddy--I don't know what I did to rile you up, but it wasn't intentional, if that helps.

  • wwestwwest Posts: 10,706
    "...left brained...."

    Would my wife resent that statement??

    In any case a little personal history.

    I walked out of Boeing, forever, one night in....aaah...1968, I think. Bummed around for two years, two jobs each of about six months. And then in June of 1969 I hit the jackpot.

    Went to work for a company selling Applied Dynamics Analog computers and they had just signed on to sell the NEW Data General Nova 16-bit DIGITAL minicomputer. They needed a field service technician on board and I was IT.

    Remember 1970's: "would someone please turn out the lights as they leave Seattle" as Boeing sales went into a serious decline and the layoffs began.

    So the company I worked for at the time closed their Seattle office. My wife and I really liked the Seattle area and while there were no jobs available there was "piece-work" available. So I bought myself a Tektronix Oscilloscope, a digital voltmeter, and some other tools of the trade and went to work.

    We incorporated the company in 1974.

    Basically what happened was that I was so good at my craft, trouble-shooting problems, failures, in computer systems that we were able to use the company's surplus funds to develop our own line of products.

    "...But please, try to stick to one thing for a little longer because because bouncing a flood of ideas around tends to throw things off kilter..."

    You're not just preaching to the choir, you're preaching to the MASTER!

    If you're ever in the Seattle area sometime I hereby invite you to come by and meet a few people that use a "flood of ideas" to help resolve computer systems problems someone may be having, say in the UAE, or even NASA in trying to maintain communications with a space probe over 8 billion miles away.

    Google for:

    Osprey SETI "pioneer 10"
  • Hylyner, my post was most assuredly not directed at you and if it seemed that way I apologize. I enjoy your posts very much. My post was directed at the other end of the spectrum for continuing to post about an issue that may not even exist.
  • billranbillran Posts: 113
    If this were the case it would account for any post you might see that just went on and on in circles, mindlessly repeating the same message over and over and over and....

    A very astute observation grandaddy. There is no doubt in my mind that there is something going on here. There is no other logical explanation for it. There are posts here with the obvious intent to amplify this topic as much as possible and I can only speculate at the reasons. I find it sad that Edmunds allows it to continue.
  • scoti1scoti1 Posts: 676
    Maybe they have been looking at the wrong problem. The "normal" "protect the drive train" designed in engine/transaxle delay/hesitation, and not even realizing that there is a RARE ABNORMAL one.

    You are definitely "thinking outside the box" and that is what needs to be done here. I think you may be on to something. This certainly makes sense when you have "my car has no problems", "my car hesitates but it is not bothersome or dangerous", and "my car hesitates 2 seconds or more and is a safety hazard". Keep those wheels turning.
  • user777user777 Posts: 3,341
    there's much to be said about non-linear reasoning, and when a problem or solution space is wide, to start wide and shallow before going narrow and deep is a good approach.

    to hylyner's point: its also good to stay focused. ;)

    i'm listening for your feedback on testing hylyner.

    from very near the beginning, i believe alot of speculation as to what was actually occuring could be captured using the OBD-II interface. No one is really hot on that idea, and I don't know why. But the recent suggestion for someone to test to see if accelerator pedal calibration upon startup is a possible contributor is a good one, simple, no cost, and can be done by numerous people.

    i personally don't go all over the map - but I don't know as much as WWEST does about these systems; he has all the manuals and has spent time reading them! he's helped a lot of Edmunds posters in other forums. Look and see.

    i have a lot of respect for what WWEST and his company does. i've googled him long ago and know we owe him a great deal for remaining in contact with a forward journeying representative of our scientific community.

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 58,488
    This discussion is taking a temporary time out, as per previous notices on the subject of constant bickering.

    We'll probably start it up again once everyone has taken a good long break.

    thank you for your participation, and please enjoy the other discussions, or if you wish, correspond through e-mail or, better yet, set yourself up a personal page at our new feature

    where you can link to other "friends" and other discussions, and also have your own mailbox there.



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