By on February 1, 2010

Update: a portal to all of TTAC’s articles on the subject of Toyota gas pedals is here:

We’ve taken it apart, explained Toyota’s intended fix, and now we’ve replicated the “fix” to see what effect it has. It works, but does it work too well?

In the photo above, the two friction teeth are shown in their operating position before the “fix”. One can easily see their pivot axle sticking out to both sides, in a lighter gray color, just where the friction unit protruded from the housing. The other end of this friction unit is the retainer for the return spring, and this is what creates the pressure on the friction teeth.

The second picture (above) shows the other end of this unit. The round end in the middle of the unit is where the coil spring is retained. The gap as shown in this picture is where the metal spacer would go. It would change the fulcrum angle, and the amount of pressure that the spring would exert on the friction teeth.

In the third picture (above) we have inserted a 1/8″ thick screwdriver shank to simulate a spacer in this area. We don’t know yet what thickness the Toyota space will have, so this is an arbitrary guess to see the effect. The amount of friction was substantially reduced by this increase in the gap, and the change in the fulcrum angle of the friction bar unit. We were not able to actually install the unit in a car to see how it would feel, but the change in feel was very noticeable to the hand.

As we’ve explained in the prior post, the balance of friction to the control spring is what creates a stable, yet safe pedal assembly. By reducing the friction, the pedal will feel “less stable”, and it might be more difficult to maintain a steady throttle opening. The perceived pressure felt by the foot will also be greater. The degree of this affect will of course depend on the thickness of the spacer Toyota specifies.

Undoubtedly, this fix will profoundly reduce the likelihood or possibility of the pedal being stuck or slow to return. But the trade off may not be immaterial. Undoubtedly, Toyota’s intended degree of friction will be compromised by this fix, to one degree or another. And drivers may find the fix unpleasant or uncomfortable, also to some degree or another. Clearly, this fix is a band aid to fix the intrinsic limitations of this design. We will be taking a closer look at the Denso pedal next to see how their design is different.

Update: The final article in this series compares the two pedals (CTS and Denso), and makes a recommendation. Link here.

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47 Comments on “Toyota Gas Pedal Fix Simulated: Friction Reduced, But By Too Much?...”


  • avatar

    Paul,

    It shouldn’t be too hard to get some shim stock or even washers of varying thicknesses and a tensiometer to see the actual differences in reduced tension.

    • 0 avatar
      Paul Niedermeyer

      Ronnie, my access to these units is highly limited. I would have like to do what you suggest, but ultimately, it doesn’t make much difference. Any shim is going to reduce friction and change the feel of the pedal; until we know what size Toyota uses, it’s speculation. It’s  a band-aid on a flawed design.

    • 0 avatar
      sean362880

      Agree it’s a band-aid. And I’ll bet the public will see it the same way, especially when their Camry’s gas pedal feels like a pogo stick.

      If the Denso unit doesn’t have this issue and it’s interchangable, why don’t they just replace the whole assembly? It’d cost more short term, but they would lose fewer customers.

    • 0 avatar
      Contrarian

      I doubt the shim will be anywhere near 0.125″. I would guess a 16th” at the most.

      Regardless, has anyone pointed out the safety factor you would get from having amnual tranmission in these cars? Just push in the clutch if the throttle sticks!

      It occurred to me because my son drives a manual Solara. Didn’t see the Solara on any recalls, maybe they are all Denso.

    • 0 avatar
      mewzikgal

      I have just had the recall repairs done to my 2008 Camry that has 8990 miles on it. I want to say that I cannot feel any difference after the repair. The accelerator pedal feels the same and I am not having any problems. (I was not having problems before the recall either). For now, I would have to say that I am satisfied. I must admit though, that I AM a little nervous and am driving cautiously. Time will tell. However, for now – so far, so good! The service department at my dealership said that they have had no problems in any of the cars they have fixed and that they have been getting positive and very satisfied feedback from customers so far. I have been a Toyota owner for the last 25 years and Toyota has always stood behind their cars. This incident will not stop me from purchasing Toyota’s. Many years ago, my husband had a Ford Pinto with the exploding gas tank. Ford had problems with exploding tires. All manufacturers recovered – Toyota will too. No one brand is immune from problems.

  • avatar

    This is not going to solve the engine’s computer failures. I believe this is a smoke screen to mask a severe electrical malfunction related to the engine. Toyota is probably now in the background somewhere working on this “real” problem, while they distract the public with this phantom break problem.

    • 0 avatar
      baldheadeddork

      I agree. If this is the (this time we really mean it) cause, how does it explain the UA problems in cars with the Denso unit that doesn’t have this design? Like, the ES350 in the Saylor crash that blew open this story?

      That’s a very basic question our press should be asking.

    • 0 avatar
      YotaCarFan

      The ES350 that killed Mr Saylor accelerated due to an incompatible unsecured floormat riding up over the gas pedal. So, the Denso pedal was not implicated in that crash.

  • avatar
    Lavventura

    In this case its better safe then sorry from Toyota’s perspective, which is why I’m assuming they gave it a good deal stiffer response.

    Though I think most Toyota drivers like the mushy Toyota pedal, personally, from my very limited experience with Toyotas, I’ve never been a fan. So it actually may be an improvement to some degree.

    It would be interesting to see by what degree the pedal is harder with the actual shims they put in.

  • avatar
    Gardiner Westbound

    Don’t understand why Toyota, while the car is in the shop, isn’t reprogramming a fail-safe into the vehicle electronics so simultaneous accelerator and brake application restricts the engine to idle speed.

  • avatar
    Odomeater

    The “feel” is the feeling of Toyota tumbling in a downward spiral. We are here right now witnessing the beginning of the end.

  • avatar

    Hey, who knows, Toyota drivers might love being further disconnected from the feedback from operation of their vehicle. This could be a new marketing point for them!

  • avatar
    guyincognito

    Paul,

    Have you tried to reproduce the failure? I would be curious as to how much pressure it takes to lock the system up.

    • 0 avatar
      Paul Niedermeyer

      According to Toyota, it has only happened on older units with considerable wear. Pressure isn’t what causes it to stick, just when the built-in friction from the system becomes somewhat greater than the reacting force from the spring. There’s no way to replicate a failure unless one had one of the bad units.

    • 0 avatar
      baldheadeddork

      Paul, any chance of tracking down the mileage on some of the cars involved? A 2008 Avalon owned by fifty-somethings and a dealer loaner ES350 don’t seem candidates having a lot of miles on the clock.

    • 0 avatar
      YotaCarFan

      Just based on looking at the pictures of the spring with its thick metal coils, it *appears* to provide a lot of force, meaning that to jam the pedal the rubber either needs to (1) be very grippy, or (2) it needs to wear out easily.

      I’m curious (1) whether the rubber feels grippy or hard, and (2) how sturdy it is (e.g., does it disintegrate like a pencil eraser if you rub it back and forth on a smooth table).

    • 0 avatar
      Patrickj

      This fiftysomething is racking up about 700 miles a week right now.

  • avatar
    chuckR

    Picture two – close-up of the friction teeth is also interesting for the ragged state of the opening in the housing that the friction/spring retainer arm passes through. How old is this sample? Did it really get molded that way?

  • avatar
    Bozzie

    Paul,

    Great series of articles on this issue! Your in-depth explanations with tear-down photos clearly explains the problem, its cause, and Toyota’s proposed fix.

    Also, seeing that tiny, offending friction contact patch in one of your photos is a graphic reminder on just how many parts and subassemblies have to be designed, simulated, and life-tested to get the high level of reliability we consumers and TTAC readers usually take for granted. The automakers who lead the industry in reliability (I hope Toyota retains/regains their reputation) really are doing some impressive design and manufacturing work.

  • avatar
    gobosket

    I agree this is not the end of the UA issues. This “fix” certainly does not apply to all the incidents where the vehicle was sitting stopped at a red light or stop sign with the driver’s foot on the brake when the UA occurred. Also, Tacomas are not in this latest recall, but the vast majority of the Tacoma incidents reported to the NHTSA ODI were for UAs.

  • avatar
    The7

    Paul,
    I think if you remove the little ridge the pedal could be stuck due to the excess friction in the grove contacts.

  • avatar

    This is the only place I could find details on the pedal!
    I wonder if the patent at website below is related. I was trying to find the details through patent search on google.

    http://www.google.com/patents?id=X_4DAAAAEBAJ&printsec=abstract&zoom=4&source=gbs_overview_r&cad=0#v=onepage&q=&f=false

    I suppose I should get rid of my super strength shoe magnets just in case :)

  • avatar
    ttacfan

    Back in ’99 – ’01 I played some PC car racing games. I bought a cheap steering wheel and pedals set but had to toss them and upgrade because of the unnatural feel. Even the more expensive ones did not feel realistic enough. Back in ’08 I was shopping for a Vibe and was surprised how game controller-like was steering on the ’09 model. I don’t remember particular displeasure with the pedals, but I have a sneaking suspicion that all those drive-by-wire systems made cheap/moderatly priced modern cars feel like they are driven with a PC wheel/pedal controller.

    I wonder if a higher end game controllers can just go ahead and use real automotive parts
    :-(

  • avatar
    Greg Locock

    Bear in mind the pedals you use for your PC probably cost more to make than this thing, which has an expected life of 10000 hours or more.

  • avatar
    mfgreen40

    I have never owned a Japenese car but my next one might be Toyota because I think they will build them better than ever and in the (past) they have built some very dependable cars. How this is handeled means everthing and they have had Detroit to show them how not to take care of a problem.

  • avatar
    Britlass

    Do any of you have any stats as to what percentage of cars with CTS pedal have had this unintended acceleration as opposed to cars with the Denso pedal? (not including the cars with the wrong floormats).
    I should be relieved that my new Rav4 has the Denso part but I’m not :( Sounds like there’s more to it. Doubtful that it is a software glitch – as someone pointed out it would go wrong from the get-go. The theory about interference from other things like towers is scary. Do other non-Toyota cars have this problem but just less frequently?
    Sometimes problems like this are a combination of several things all coming togeth at the right (wrong) time. Like when a plane crashes, it is never just one thing but a series of events.

  • avatar
    shaker

    I wouldn’t totally rule out software (firmware, actually) at this point – even an 8-bit system with multiple parameters can still see millions of combinations of data, where only a select set could cause a “crash”. The likelihood of such failures is very small, but a “perfect storm” scenario where rare and unforeseen data cause failure of a software program are almost always exposed in the consumer’s hands, the ultimate test.

    The few cases of UA that have been reported to happen while people were coming to a stop with their feet off the gas and on the brake may be hinting at this, though the reports are still spotty (and obviously denied by Toyota at this point).

    Ask Microsoft…

  • avatar
    csf

    Sorry, but I also do not believe this simply a mechanical problem with only the CTS pedals – there are now reports of 2009 and 2010 Camry’s crashing. How much wear can really be on a pedal only a year old, even if it is the CTS unit? Are they that poorly designed and built that they won’t last a year? I doubt it. And isn’t it unbelievable they threw poor CTS out there – I can’t remember the media ever blaming the supplier of any part recalled by GM or Chrysler.

    Instead, I also believe there must be a software problem they are working on but will not admit. Of course, I have good reason to be skeptical of Toyota. I had a V6 Camry over 10 years ago that suffered a complete engine failure after 46,000 miles. My dealer and Toyota blamed this on me for performing my own oil changes, which I had always done.

    They wanted $8000 for a new engine installed, which I could not afford. So I had to trade the Camry, not running, on a used Ford Contour, and roll the $5000 I was now upside down on the damaged Camry into the Contour loan. I paid way over book value for that Contour so the Ford dealer would take the Camry off my hands.

    Years later, after thousands of V6 engine failures in many vehicles, class action suits and government investigations, Toyota admitted they knew their engines were running too hot, baking the oil and causing the engines to sludge and fail. They were forced to reimburse owners for their engine repairs – but I got nothing because I didn’t repair my car and had no receipts to submit. I lost over $5000 on that Camry after only 46,000 miles.

    Toyota will never see another dime of my hard earned money. And based their past actions, I fully believe they are hiding the full truth about these sudden accleration issues. Over the past decade, despite Consumer Reports’ bias, Toyota has cut corners, cut quality, and been dishonest and quick to blame their customers when problems occur. I feel terrible for the current owners who have been injured or even killed. But Toyota is getting what they finally deserve. Maybe more Americans will think twice now before they blindly walk into their local Toyota store and put down their money without even considering another brand.

  • avatar
    bfs

    I do NOT believe that Toyota is forthcoming. I’m perplexed why I don’t see any facts concerning the PROBLEM OF SUDDEN UNINTEDED ACCELERATION. All the media and coverage has reported that vehicles are accelerating at red lights and jumping curbs through storefronts. Yet, sticky or slow pedal experience in remote instances of the CTS pedal does Not address the sudden unintended acceleration syndrome. It is a fact that the sudden unintended acceleration has been reported to have existed in some Lexus vehicles and Toyota vehicles going back to 1999 which is way before CTS even became a vendor for Toyota. So, why is no one investigating the facts of the reported unintended acceleration issues?????

  • avatar
    RichB in AZ

    Here’s my take as to why this is happening. (I do design engineering as a day job – turbine components.) The links go to Toyotas site if you doubt them.

    This is an example of really poor design. There are a couple of things to look at on the Toyota site – this video

    http://www.toyota.com/recall/videos/pedalassembly.html

    Shows how this fly by wire pedal works.

    Notice the “designed in” Friction device, supposed to replicate the feel of a cable operated pedal – Why?

    There is also a picture showing where the pivot points are on the devices – here… (download the larger one)

    http://pressroom.toyota.com/pr/tms/photo.aspx?fid=93538&id=E0C18554

    The circled views are top looking down views, the ones below are side views. The whirling propeller symbol is a pivot on the friction device. It’s in the wrong place for a failsafe system!!!

    When the pedal is pushed down and released, the V shaped grooves rub on the turning pedal pivot. Pushing down on the pedal is a trailing rub on the spring loaded friction device, not a problem. Lifting your foot off puts the rub device in a leading pattern – bad. Like twin leading shoe drum brakes (for us old timers)

    Think of it like working a broom. Put the broom on a smooth concrete floor and pulling the broom backwards over the floor is easy (pushing pedal down). Pushing it forward is a bit harder… the forward push is similar to the pedal being released – Leading friction arm.

    Now say that wear debris and moisture have changed the concrete floor to carpet. Pulling the broom back (=pushing the pedal down) is still fairly easy. Pushing the broom forward on carpet, it ain’t happening (= releasing the pedal)Don’t belive me, go try it.

    That’s why it sticks.

    To make matters worse they use tapered edges which enhances the friction and jamming effect – just like a morse taper on a machine tool spindle. This looks like a pure CTS issue – except Toyo should have seen this when they reviewed CTS’s drawings.

    What about the shim???
    It is supposed to limit the amount the wedges self jam. Or eliminate the rub entirely.

    My recommended fix??!!??!!??

    Cut the friction arm off. We don’t need no stinking friction arms!
    Or replace it with the Denso Pedal. (the shim is cheaper than the $12 pedal??? – that’s why they are doing the shim. But sometimes it’s not about the money.

    Can the shim come out on it’s own? what if it rusts in humid conditions and throws more debris into the friction device?? How thoroughly has this been tested in the 2 week time period since they anounced the fix???????

    Looking at the pictures of the Denso Pedal, which my ’09 Xb has, It appears to be a sandwich style friction device – can you confirm that with your dismantled part?

    The sandwich style is a better design with no self jamming tendancies. If it gets stiff pushing it down that same stiffness will be there on release.

    This does not address sudden accel, but with fly by wire, anything can happen. This one issue is mechanical in nature.
    Rich

    • 0 avatar
      The7

      Rich,
      This is the best explanation about the sticking in the recalled CTS pedal.
      Thank very much.

    • 0 avatar
      Paul Niedermeyer

      You’re largely confirming my own take, except your suggestion to get rid of the friction arm. That would be a huge problem; without some built in friction, the fatigue of pressing against the spring would be very objectionable, and it would make it difficult to keep the pedal at a steady state for any length of time. All pedals have built in friction (hysteresis) for this reason. It’s a must, but it can be done in a much more elegant way than the CTS friction arm.

    • 0 avatar
      Robert.Walter

      I’m only going from Paul’s pics, but IMO, in the Denso assy, one side of the hysteresis curve is due to the spring pair trying to buckle within the curved slot as the driver presses the pedal, rather than being squeezed between lid and housing as the lid is screwed on (the spring kinda snaking-out to its max confined length as the driver releases the pedal is the other side of the hysteresis curve)…

      In this way, the design would be robust against any wear (oriented front-rear in vehicle) between the slot and the spring, which would not be the case if the spring was pre-loaded from side to side by clamping the lid onto the housing (in addition, both lid and housing would be under continual stress, and subject to those bad things that happen to plastics under continual stress), and if there was no pre-load, wear on the laterally oriented surfaces of the outer spring, lid and housing (or any number of other tribologic influences) would reduce the pre-load, damping, and hysteresis effect.

      Hopefully the kind of testing which did not detect the design’s lack of robustness to moisture in the first place was not repeated (but was upgraded to take into account temp & humidity).

      I have to agree, I have been wondering what unintended consequences will come out of the shim-bar fix … will the new orientation of the teeter-totter cause the plastic to fatigue, or gall, will (as you pointed out) the bar oxidize and be a new source of debris?

      My guess is that the bar was not so much a cost save, as it was an expedient way to get as many cars fixed as possible without having to add production capacity to produce a lot of pedals over the short-term, and to have a fix that will allow them to begin selling cars so they can resume production as quickly as possible without suffering from a constrained pedal supply).

      Also, AP reported today that GM was shipping parts to its dealers for the Vibe … I was left with the impression that these are new replacement pedals, not repair shim-bars… can anyone confirm if GM is doing a pedal replacement rather than a repair? If so, this would be very interesting and potentially telling!!

    • 0 avatar
      moondawg

      Although, I appreciate the theories and perspectives brought here by others, it is my belief that there is a much simpler explination to this undesireable situation being encountered by Toyota and the consumer. It is called Variation! Wether it be in the relational distance of the pivot points to the geometric configuration of the frictional interface. I believe that dimensional/geometric variation is the main root cause here. Also, this is in my opinion is a poor design, with the use of the two tooth and groove geometries. . Functionally, I fully understand the desire to have a variable friction function for the “feel”, just think they dropped the ball on this particular design, there is definetly room for improvement.
      Shimming is a popular correction, not solution, to the effects of variation and the undesireable functionality of a design such as what is being observed here. I am not completely buying the explination given by Toyota, that the root cause can be traced to material selection or environmental variables. Yes, these of course can be contributors. However, because this effect is being observed in cars new to old, time does not appear to be a main contributor here.
      Additionally the previous explination as to the effects with a broom and concrete may give some a better understanding of friction and some contributors to the desired result, it is not necessarily a good example of what is taking place here. Why you may ask, well because the broom is not constrained or fixed like the friction lever is. I do agree that this “fix” could introduce additional varibles which could cause further issues, but I would be more concerned that one thickness solves the whole problem. Since the “fix” is basically removing the functionality, it presents further issues such as the “springy or bouncy” pedal as described in the posting after this. So I believe we will continue to hear more complaints until an actual “corrective action”, not a correction, is implemented.

      Further more the “fix” itself further lends credibility to my theory, that is that this is a dimensional variational issue, since they (Toyota) are adding a dimensional value of thickness to take out the issue. I would be very interested in knowing what the results of the FMEA were on this design. It leads me to questions like, was this critical characteristic identified and if so was it properly communicated throughout the development process. More importantly if it was, do the tolerances on the drawing reflect this? Was tolerance analysis conducted on this assembly? Were the components manufactured to spec and did this spec take into consideration impact of variation to the functional intent? All and more of what I’m saying is well known in the automotive industry and if there is compliance to TS 16949/QS 9000, not to mention robust design practicies, this should be traceable thru proper documentation procedures! In the end this should all come out, wether we the public hear what the actual “root cause(s)” are is another issue.

    • 0 avatar
      mewzikgal

      I was told by Toyota that the Denson pedal and the CTS pedal are completely incompatible – like putting a 3 prong plug into a 2 prong outlet.

  • avatar
    cvtundra

    Great article! I love my ’07 Tundra! I just had the pedal recall repair done 5 days ago. From the second I drove it off the lot I noticed the feel of the pedal was very uncomfortable. It’s like driving with a hair trigger. When I hit the slightest bump in the road the truck accelerates because the action on the pedal is so light it’s hard to keep the RPMs stable. Toyota has a BIG problem here. This fix is NOT adequate. I predict it will cause more problems than it solves. On a really bumpy road it will be almost impossible to maintain even speed or RPMs with this fix. I hate the feel of the pedal action now.

    VERY BAD FIX…PERHAPS TOO HASTY ON TOYOTA’S PART. I’m going to demand that Toyota get this fixed right!

    • 0 avatar

      My 2010 Tundra had the pedal fix done four or five months ago. It was a lousy hair trigger before and it is no different now. With 42000km on the truck the pedal and the bad accelerator delay are the only problems or complaints I have with this otherwise very excellent truck.
      I wish the auto manufacturers would leave the driving to me. I cant stand a computer second guessing what I want the vehicle to do. I hate going to the steelers and getting the diatribe about throttle by wire every time I go for service and make them write on the service report my complaint about the terrible throttle assembly. Its like they have a legitimate excuse because they have a system that us poor laymen cant understand. My response is that I own three vehicles with the same kind of set up, and the toy is the worst of the lot. Gas pedals have been in cars for over a hundred years that have worked just fine and Toyota has distinguished themselves as the company that has screwed it up.
      Has anyone had a proper fix to their gas pedal or throttle delay?
      Has anyone had any success with chips to get better throttle response?

  • avatar
    Mattsky

    My Pontiac Vibe was part of the recall. It’s a joint GM – Toyota car. The Toyota version is the Matrix. After the recall work was done I felt no difference in the gas peddle.

  • avatar
    downessr

    Does anyone know if this fix affects accelleration? My 2009 5 speed manual(not fixed) was much quicker than my 2010 5 speed manual.

  • avatar
    downessr

    The 2009 had 28k on it. The 2010 has 1700. The pickup in the higher gears is no way near the old one(which was unfortunately totaled in an accident).


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