By on February 28, 2010

Call it the ultimate of ironies. Yesterday afternoon I headed to the Toyota dealer in my 2005 Toyota Scion xB for the purpose of shooting photographs of various Toyota gas pedals to see why certain models seemed to have a higher rate of UA complaints to the NHTSA. In search of some intended acceleration, I headed up the up-hill I-105 connector on-ramp at Washington Street at full throttle. As I lifted my foot off the accelerator pedal, it stayed wide open…

My first thought was to call Stephanie on the cell phone to hear her voice one more time Since my car is a stick shift, that happened at the same moment my foot also pushed in the clutch. The engine quickly revved to redline, and bounced off the rev limiter. I instantly gave the gas pedal a quick sharp jab, and it fell back to idle. The whole incident lasted between one to two seconds. I shifted into third, and was on my way.

What happened? I’m not sure, but here’s what didn’t happen: it wasn’t a “sticky e-pedal” since the Scion has an old fashioned throttle cable. It wasn’t floor mat entrapment, but it sure could have been before I cut the whole front section of my all-weather rubber mat off. It has a huge lip around the edge, enough to contain a small lake of melted snow or mud. But I had serious problems with it getting in the way of my pedals when I first bought the car (used) three years ago.

The mat constantly interfered with both the gas and clutch pedal. I could deal with the gas pedal, by quickly shoving the mat to the left with my foot, and it didn’t really ever “jam” the pedal wide open. It tended to just get in front of it, and slow its return or just generally get in the way. But the mat kept the clutch pedal from its full travel, which may have contributed to harder shifting. I quickly got tired of the mess and cut the whole front section of the mat off. I don’t know if these are Scion/Toyota mats, or aftermarket. The have no retaining mechanism or any identifying mark, so I suspect that they’re aftermarket.

I had installed an aftermarket cruise control (myself), but that was turned off. [Update:I’m 99% certain it wasn’t the CC. I installed it myself, and understand its mechanical relationship to the throttle. It’s designed well just to avoid this type of problem. It has a long open slot, in which a pin from the throttle rides in, so that if the CC is not engaged, it can’t hold back the throttle; a good fail-safe design. I’ve checked it out again this morning, and all of the CC and throttle linkage are working perfectly and freely, and I can’t really see how that could be it.]

The throttle pedal, cable and throttle assembly itself all seem to be fine, in checking their action and their return springs. It certainly wasn’t a case of pedal confusion. The first signs of a deteriorating throttle cable? A sticky throttle mechanism, which was implicated in Toyotas (and other cars) back in the late eighties and early nineties, due to carbon build up? Changes in gasoline formulations supposedly ended that. A one second demonic possession? Shit happens?

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54 Comments on “Toyota Unintended Acceleration Experienced First Hand!...”


  • avatar
    Facebook User

    Fortunately the combination of the anemic 1NZ-FE and a manual transmission mean that it’s not a pressing enough issue to find the root cause, eh?

  • avatar
    allythom

    Can you explain a bit more about the aftermarket cruise control ?

    Rightly or wrongly, my money, and more importantly, that of Toyota’s lawyers, would likely be on a problem with that.

    • 0 avatar
      Paul Niedermeyer

      It has to be “turned on” again every time the car is started. I had not turned it on, and it was not on, as verified by the lack of its “on” LED. Anyway, stepping on the clutch would have de-activated it, as there’s a clutch switch. And my jabbing the throttle wouldn’t/shouldn’t have made a difference if the cruise control was stuck on wide open. I really don’t think it was the problem.

    • 0 avatar
      allythom

      The reasons I suggest it may be an issue with the CC system are as follows:

      1. There is probably a mechanical element to the aftermarket system which the original throttle linkage was not designed to work with. A small amount of friction in this mechanism at the extremes of the throttle’s range of motion could be introduced over time (inadequate lubrication, wear, or corrosion could cause this) This may be enough to overcome the ability of the stock throttle return spring to close the throttle when pressure is removed from the gas pedal. In this situation, whether the system was on or off would not matter. ‘Jolting’ the linkage by prodding the gas pedal again may have been enough to overcome that.

      2. The stock CC system in my ’02 Subaru WRX was subject to a recall several years ago for a sticky throttle issue. Apparently the throttle cable from the CC controller could jump off the throttle pulley and seize the mechanism, thus causing the throttle to remain open. The proscribed solution was for dealers to fit retaining clips to prevent the cable from coming off.

      Of course, this is just theory based upon what you have told us, there could be any number of other reasons for the issue with your car. My advice would be to ensure that any other members of your family who drive the vehicle know how to deal with the issue should it recur. And to take it to be looked at.

    • 0 avatar
      Paul Niedermeyer

      I’m 99% certain it wasn’t the CC. I installed it myself, and understand its mechanical relationship to the throttle well. It’s designed well just to avoid this type of problem. It has a long open slot, in which a pin from the throttle rides in, so that if the CC is not engaged, it can’t hold back the throttle; a good fail-safe design.
      I’ve checked it out again this morning, and all of the CC and throttle linkage are working perfectly and freely, and I can’t really see how that could be it.

  • avatar
    JohnAZ

    I’m sure it must have been either you were caught in the draft of a Lincoln Town Car with real Ford UA problems, Dr. Gilbert sabotaged your throttle with some paper clips, or Mrs. Smith was behind you with both feet on her gas pedal. Either way, it couldn’t possibly be a fault of your Toyota.

  • avatar

    Were you wearing wide shoes?

  • avatar
    Don Gammill

    Assuming the throttle plate actually completely shut when you jumped off the accelerator pedal, I wonder how much of an effect a stuck-wide-open idle air control valve might have if a faulty ECM was still cycling the injectors at their previous rate?

    • 0 avatar
      Robert.Walter

      Don, I don’t think that dog can hunt … a closed-throttle plate means minimal air to the cylinders, combine that with injectors hosing fuel into the cylinders at a WOT rate, and you get a whopper of a rich-burn condition … not only would the motor not really enjoy running at a well out of stoiciometric range condition, I would think the controls system might have tossed a code into the OBD2 in-box … (thought also comes that throwing a code may also be the condition which releases the anomaly.)

      Paul, do you have the means to pull OBD2 codes?

      Personally, I would be focussing on mechanical interference, binding or wear in the aftermarket cc device either internally, or where it interfaces with the vehicles throttle linkages.

    • 0 avatar
      Paul Niedermeyer

      Robert; see my latest comment about the CC further up in the thread.

    • 0 avatar
      MBella

      The idle air control valve was sticky in my Ranger on really cold days. It was enough to accelerate the car, but not enough to be confused with WOT.

      The IAC being stuck open under a closed throttle condition would make it lean, not rich. However the ECM would compensate for it because of the MAF.

  • avatar

    I saw the alcohol gunk build-up, but usually it happens where the flow is constricted… In my case it would cause throttle stick in idle, not full. It should be easy enough to check anyway.

    If not the build-up, the cable needs some love. Or a replacement.

  • avatar
    psarhjinian

    Maybe your throttle cable got snagged? It’s hard to believe, I know, since mechanical throttle cables are wonderfully simple and never, ever have problems.

  • avatar
    Scottdb

    Three words for you, Paul:

    SUE! SUE! SUE!

    • 0 avatar
      Facebook User

      There’s no proof it wasn’t the aftermarket cruise system’s fault, or the installer of said system’s fault, unless Paul actually takes the time to find out what caused it. As allythom said above, unless the cause is proved to be not related to the CC system or a faulty installation, there’s no way to take this report as anything but speculation. Especially since the xA/xB twins are not even present on the list of NHTSA UA complaints published yesterday here on TTAC (the Yaris is present but that car DOES use drive-by-wire throttle, where the Scion twins don’t).

  • avatar
    BuzzDog

    Had this happen in a ’96 Maxima (I know, I posted this before) and I’d check the following:

    First, make sure that there is absolutely, positively nothing near any of the throttle cable fittings. My problem was caused by a mechanic who failed to properly secure the air intake to the throttle body, which caused a clip to “hang” on one of the tensioners.

    Second, make sure that the throttle body is clean…although in my experience that tends to make it stay closed, not open, but I suppose anything’s possible.

    As others have stated, might be time for a new throttle cable.

    The fact that it returned to idle after a pedal “blip” (a highly technical term) tends to support that something mechanical is sticking.

    Take care of this quickly and let us know what you find, Paul…I’ like to be able to read your writing for many years ahead!

    P.S.: The strikeout text was brilliant, and my laughter upon reading it scared the dog into the next room!

  • avatar
    50merc

    What’s certain is you deserved it because you (a) hate domestic cars; (b) hate import cars; (c) are older than Buick’s demographic; (d) didn’t know to quickly take the CV joints apart; (e) all of the above. Whatever, you should fall to your knees and thank God for intervening in your emergency faster than He did for Mrs. Smith.

    Those all-weather floor mats are dangerous. Just to be safe, I threw mine away and substituted a whoopee cushion. Safe and hilarious.

  • avatar

    If it’s not a cable snag, it could have something to do with the return spring on the pedal assembly. By flooring the accelerator, the spring would have experienced maxiumum compression. The spring may have snagged itself and developed enough friction to hold the pedal down until you jabbed it.

    A similar failure happened in two cases of catastrophic Boeing 737 rudder reversals. When investigators first analyzed the rudder’s hydraulic control modules, they worked perfectly fine –until years later when they tried to replicate atmospheric conditions and freeze-thaw cycles before the crash. The valve springs squeezed themselves beyond control limits, the resulting hydraulic flows made the module unresponsive, and the jammed rudder sent the jets spiralling to the ground.

  • avatar

    Busted the laughmeter!!!! (the strikeout. and 50merc’s whoopee cushion.) Obviously God likes you better than he likes Rhonda Smith, because he took care of you so expeditiously.

    I had unintended acceleration in the Peugeot 404 wagon after I’d been driving legally for several months. I put the car in neutral and hit the gas several times with my foot until the revs went down again. Damn sticky French throttles, it must be all that foie gras.

  • avatar
    Telegraph Road

    Paul, did you file a complaint of your alleged “incident” (quoted to mollify Bertel) with NHTSA?

  • avatar
    reclusive_in_nature

    Are you an American? The post that came out after this one hints that it’s solely an American issue.

  • avatar
    BDB

    Fools! All of you!

    Obviously, Paul’s problem was caused by the UAW, along with the Obama administration and Ray LaHood who used the electronic beams Rahm Emmanuel is broadcasting from his secret SUA Machine in the basement of the White House to cause Paul’s xB to accelerate, so he would sell his xB and go buy a Chevy HHR or PT Cruiser. Paul, put your tinfoil hat on NOW before Rahm’s beams also take over your mind and make you have a sudden urge to buy a GM or Chrysler vehicle! Fast! If you don’t, you will cause a trade war that will collapse the entire world economy. Oh, and it’s also because Paul is a drooling idiot American driver, and we all know Americans don’t know how to drive. Also, Howie Long is in on it, as well.

    Or, it could also be that Toyota has some kind of trouble with it’s throttle controls.

  • avatar
    dougjp

    A cable.

    Try and replicate it by pushing to the floor without the engine on. Then repeat using varying angles of pressure on the pedal, both left bias and right bias. A good chance the right angle will cause a hangup, because when a cable starts deteriorating it will just be a ‘nick’ internally or rubbing on something ‘just so’.

  • avatar
    TonyJZX

    you should sue

  • avatar
    Telegraph Road

    Paul, you missed your chance. If you had only driven it, by shifting in and out of neutral, to your local ABC affiliate, you would be famous.

  • avatar
    pgcooldad

    Fittingly :)

    http://file.vintageadbrowser.com/4deef62ypmh83i.jpg

  • avatar
    MSil34

    That freaks me out, cause something similar happened with the ’04 Ford Ranger I drove few years back. It’s also a manual, so I was able to use the clutch to stop the acceleration. As far as I know, the truck works fine now, but I wonder…

  • avatar
    Wheeljack

    This was all merely a figment of your imagination. The Toyota Police will be along shortly to ensure you have your story straight.

  • avatar

    It goes to prove the point I’ve made many times: NO CAR EQUIPPED WITH A MANUAL TRANSMISSION CAN BE TRULY SUBJECT TO UNINTENDED ACCELERATION.

    The instant fix is found right below your left foot.

    • 0 avatar
      psarhjinian

      It goes to prove the point I’ve made many times: NO CAR EQUIPPED WITH A MANUAL TRANSMISSION CAN BE TRULY SUBJECT TO UNINTENDED ACCELERATION.

      My wife managed to smack our old stick-shift Mazda into a pole. Pedal confusion, by the way, as are most SUA incidents.

      It is harder to have such an incident with a clutch, but I think you’re under-estimating the degree to which people do stupid things in a panic.

    • 0 avatar
      ihatetrees

      A co-worker of mine had a mechanic relative install a remote start in her well preserved, pimped out, MT Celica.
      The mechanic warned her, “Don’t leave it in gear!”

      On a cold, wintry morning, she put it thru her garage door.

    • 0 avatar

      Better:

      A few years ago, I took a friend to pick up a new Elise. His “other” ride was his F150 for work.

      I was thinking: I should caution him about pressing in the clutch before pressing the “Start” button.

      I didn’t.

      He took off the back of his new Lotus on a new Audi Q7.

      Confusion reigns supreme!

  • avatar
    NickR

    Practice crying in front of the mirror. Proceed directly to Washington.

    This might sound stunned but…are you sure your foot didn’t fall asleep and maybe it didn’t move as much as thought? I can’t remember which car it was that I had, but the seating position was such that my heal used to go numb and I had to shift round alot to prevent it.

  • avatar
    Bubba Gump

    ED
    reading about your trevail I’ll send you off to check something.However a question first. When this occured did the pedal feel as if it returned under spring force? If so the spring is around the throttle body cam and if so then it would appear the shaft rotated to raise the pedal when you took your foot off the throttle. If my assumption is true I would take the intake off the throttle body ahd while holding the cam see if you can force the throttle blade open with your finger. If the cam stays in position and the blade opens you potentially have a fractured throttle shaft. Will be intrested to see what you find. Unlikley but worth a look. The throttle position sensor on the other side of the throttle body could have also caused the potential hang.

  • avatar
    N8iveVA

    a few years ago i put a larger aftermarket throttle body on my 00 Mustang GT. Twice while at WOT it stuck open. I gotta say that’s a little scarier on a V8 than on a small 4 like the Scion. I stomped the accelerator pedal about 4 times before it unstuck. Yeah, i swapped the factory throttle body back on

  • avatar
    Jeff Waingrow

    I thinks it’s the power of suggestion. I know that often after I read a medical article, I start to get symptoms that are most worrisome and seem to point in only one direction. Could all this talk about SUA have sowed in you some altogether uncontrollable impulse, one that lead inexorably and relentlesly to your right foot?

  • avatar
    Zasdoogy

    Paul, have you checked the throttle cable to ensure that there’s no “nick”? I had been working on my Civic Si one time where I had nicked (but not remembered) the cable, and the next day had a sticking issue until I realised that the cable might have been damaged from my tinkering around in the engine bay.

    When you installed your after market CC, you didn’t happen to somehow move or tweak the throttle cable somewhere in the line? I’d check, especially near where the linkage hooks to the throttle-body. Also, make sure it’s greased just right amount, that can also be an issue.

    If all else fails, stick to the whoopee cushion from 50merc and call it a day with a cold one! (and one cushion for the passenger side as well)

  • avatar
    nova73

    Perhaps driving at WOT most of the time has caused premature failure of the throttle return spring. Does the pedal require as much pressure to depress as it once did?

    Had this happen to me on my first car. I had to pop it in neutral and coast into a rest stop. The temporary fix was to hook one end of the spring to something farther away from the carb. I think the replacement spring was a Motormite part, which means it was a commonly replaced item.

  • avatar
    gslippy

    Paul,

    This EXACT thing happened to my 05 xB (MT) in 2006. Read my post on the subject here: https://www.thetruthaboutcars.com/toyota%E2%80%99s-pedal-gate-%E2%80%9Ca-fiasco-with-unfortunate-consequences%E2%80%9D/

    I attribute the cause to frozen water in the throttle cable, thawing and subsequently re-freezing under ideal conditions. It has not happened since due to more care on my part, but it was really scary at the time.

    • 0 avatar
      Paul Niedermeyer

      I remember that. But that wasn’t an issue here. I neither washed the engine (or car), nor have we had any freezing weather. It’s been very mild here lately.

    • 0 avatar
      italianstallion

      Me too, in my ’04 Xb: https://www.thetruthaboutcars.com/toyota-floor-mats-absolutely-positively-100-certainly-the-problem/#comment-1559284

      I was pretty certain it was the floor mats the first time. The second time, I was less certain. Both times it was under hard acceleration entering, or changing lanes on the freeway. And both times, I immediately engaged the clutch, turned off and restarted the car while still moving. Freaky.

  • avatar
    Detroit-X

    Paul,
    Take a look at the air intake valve that the gas pedal actuates (butterfly valve?). At certain temperatures, it may stick in wide open or closed postions inside the throttle body. This happened to me with a Subaru I owned (worst POS ever), sticking in the closed position at cold start-up. When warm, and after first push, the trottle worked fine. After cooling overnight, at the first AM start-up, it would stick and go ‘pop’ the first time you pressed it. Apparently a mismatch in size, or metal compounds (thermal), in the throttle body. I took a file and shaved off the offending edge at the closed position, and it never happened again. Worst POS ever.

    For your Scion, and maybe these Toyotas, the butterfly valve may stick in the wide-open position (at a certain temperature range only).

  • avatar
    John Horner

    Wow, Paul seems to have joined the Trade War Conspiracy! LOL.

    Now, back on planet real: Assuming the throttle cable is in tip top shape, my bet would be a sticky throttle body.

  • avatar
    cdotson

    In a former job I worked on developing the pull-cable mechanisms for the throttle on an off-road 4×4 vehicle. In that environment there is greater concern for sticking cables (and I saw my share during development).

    What is most likely to happen absent a visible mechanical defect like a broken/nicked/frayed cable is that the seal at one or the other end of the cable has slipped off allowing dirt intrusion. Once dirt gets between the cable conduit and the cable itself it will get sticky and the plastic inner lining will become scuffed and begin dragging on the braided cable.

    Check the engine end of the cable and there should be some form of rubbery “boot” or bellows that snaps onto the fixed jacket and is tied or crimped onto the braided cable. This seal prevents a section of the braided cable that is exposed to environmental contamination from ever entering the jacket. If the seal/boot slips off the conduit or the crimped end loses its crimp and stops moving in unison with the cable the seal becomes compromised and dirt can intrude on the cable.

    A compromised (or inadequate) seal is also what contributes to freezing cables. A cable design should pass a freeze test where the ends are sprayed with water and taken to at least -20 F without freezing. If it freezes, there wasn’t enough seal at one end.

    Usually cables don’t just wear out on their own. They’re helped by dirt and/or water. The exception to this is cables that have die-cast metal ends on them of various sizes/shapes. They’re usually zinc which isn’t very strong, and if the size and shape of the zinc connector is such that the braided cable cannot be cast continuously throughout the end (usually a “Z” type end), then the end of the braided cable is intentionally frayed into a ball for the zinc to cast into while the remainder of the connector is solid zinc. This point where the cable frays becomes a stress concentration and the zinc end tends to crack through and separate at this area unless the mating piece is designed so as to account for this cable feature.

  • avatar
    OMG_Shoes

    I’m inclined to second Detroit-X’s somewhat foggy comments: check and then spray-clean the throttle body and plate. A buildup of fuel gum on the throttle plate, body, and shaft can at certain temperatures be extremely tacky. In the old days this gum used to prevent automatic chokes from working correctly, but the throttle plate on a carburetor or TBI system is wet; always being washed down by fresh fuel. The throttle plate on a port fuel injection system is dry, so there’s nothing to wash down the gradual gum buildup that forms from fuel evaporation after shutdown. There’s not much fuel in the intake tract after shutdown, but there’s some, and little by little…

    Anyhow, check it out. Oh, and what make and model of CC did you install? I’m after one myself.

    • 0 avatar
      Paul Niedermeyer

      I’m pretty sure it was the Rostra, although this one looks abit different. Maybe it isn’t the right picture. Works perfectly.
      http://www.nulime.com/Rostra-2501732-2006-2008-Scion-tC-XB-XA-2005-2009-Toyota-Sienna-2006-2009-Toyota-FJ-Cruise-Control-Kit/p449294

  • avatar
    JackHammer

    Paul, always enjoy reading your articles. I’ve had a similar experience with a cable throttle, manual transmission car and thought I might offer one more suggestion. With mine, it was neither the cable, the pedal, nor anything external to the throttle body at fault. I too could usually fix the issue by jabbing the throttle. When I finally had reached my wit’s end and was replacing the TB, I removed the throttle position sensor to swap it over to the spare TB. I found small chunks of aluminum jamming the dog on the throttle pivot inside the sensor housing, because a bolt 3mm too long had been installed to affix the TB bracket and pushed the material at the back of the blind hole into the housing. It was even an OE bolt, just used in the wrong hole by the previous owner. This also coincidentally fixed a rough idle I had previously considered unrelated, because they were jamming the sensor partially open as well. Just something to consider; even in the most well-thought-out (factory) systems, a few millimeters can make all the difference.

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