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Toyota and Lexus floor mat recall (unintended acceleration problems)

October 4th, 2009 · 6 Comments

Toyota Motors and and the US National Highway Traffic Safety Administration (NHTSA) recently announced a recall of 55,000 floor mats for various Toyota and Lexus models following an investigation into a crash of a Lexus ES 350 on 28 August 2009 that killed a 45 year old police officer and three family members. The car sped out of control and finally hit another vehicle. Suspicions center on an All-Weather floor mat that could have got entangled with the accelerator pedal.

Floor mat problems in cars are not that uncommon. My previous car was an Audi A4 and there the mats provided by the dealer (it was a second hand car) did not fit the nipples meant to match up with holes in the mats. As a result, the driver side mat always kept sliding forward under heel pressure and sometimes ended up under the pedals (luckily never over the pedals!). One day my wife and I wondered why the car suddenly had a hard time accelerating (it felt really sluggish), until I realized what had happened and pulled the thick mat back out from under the accelerator pedal, which could not be depressed properly (presumably braking would have been similarly affected, but luckily I did not have to find out).

The opposite problem of unintended acceleration tends to be far more severe than a lack of acceleration, of course. An accelerator stuck on full throttle is something that happened to me once while driving a VW Santana, back in the 1980s.

That 5 cylinder engine still used a carburetor, not fuel injection. At some point the cold start enrichment mechanism of the carburetor developed a problem. I reported this issue to the dealer before a service and asked them to fix it. I don’t know what they did about it, but the next weekend I took the car on a German autobahn and had a very unpleasant incident where it got stuck at full throttle while I was doing over 160 kph (there was no speed limit there).

I found that the car kept accelerating even if I took my foot off the pedal and reached about 180 kph. I then pushed the brake pedal as hard as I could and at least it didn’t accelerate any further and slowed down a little. I depressed the clutch pedal (the closest manual equivalent of putting it into Neutral). Without any load on the engine, the RPMs shot up to the max but were limited by the engine management. With the engine roaring at maybe 5800rpm, the car coasted on the straight road and the brakes could slow it down. Worried about the engine I then switched off the ignition, which did stop the engine but also disabled the brake servo and power steering. I quickly turned the ignition back on, but not far enough to engage the starter, just so the steering lock could not be activated by turning the steering wheel as it would with the ignition completely off. I finally brought the car to a complete stop on the hard shoulder, without brake servo assistance.

After opening the bonnet, I opened the carburetor with a screw driver from the emergency set in the back and found the butterfly valve stuck. After some prodding with my fingers, it went back to the proper position and I could resume my journey, with no further incident.

I can see that using the brake pedal, my first reaction in that situation, would not have been as effective in a 3.5 litre V6 Lexus as it was in my 2 litre VW, because the engine was far more powerful. Switching the car to Neutral, my second reaction, would have been quite effective in the Lexus though. My third reaction, switching off the engine, would have been quite impossible for the average driver in that loan car. Turning off an ignition key is one thing, but having to hold down the power button for three seconds (as in that Lexus and some other cars that use a start button instead of an ignition key) rather than just pushing it once is anything but intuitive. Yes, mobile phones and computers can be shut down that way too, but most of us grew up with cars that behaved differently from today’s computers. Actually, even when I started with computers they switched off as soon as you pushed the power button once. I can see how the driver would push the power button once to turn it off and nothing would happen. Then what?

If the driver missed his chance to shift the gear into N, he would likely run out of time in that car before hitting another vehicle in front, before he would have figured out how this is supposed to be done.

Most accidents occur due to a combination of errors. In this case it appears to have been the floor mat problem, combined with the driver missing the chance to respond effectively by shifting the gearbox to N.

Problems with stuck accelerators could have been ameliorated in the engine management by having the brake pedal override accelerator input. If for example the brake pressure was high enough for an emergency stop (the ABS has a sensor for that) then the fuel injection quantity could be limited to idling or at least significantly less than full acceleration would demand, effectively ignoring the accelerator, floor mat or no floor mat. The only side effect I can see is that it would make drag racer starts impossible.

When I explained about the recent Toyota problem to my wife, she replied that she had tried to remove the mats from our 2008 Prius for cleaning but didn’t manage to because the hooks held them in place too firmly. Even without the hooks I imagine the left foot rest in the Prius would stop the mat from moving much.

Whatever car you drive, make sure the floor mat is secured against sliding around. If you’re not sure, better get rid of it altogether. And if you should ever find yourself with a car accelerating out of control for whatever reason, remember that the N position of an auto box or clutch pedal of a manual will always disconnect the engine from the gearbox, not matter what causes the engine power to surge.

Tags: cars

6 responses so far ↓

  • 1 Joe Wein // Oct 25, 2009 at 17:58

    Three days after my blog post that proposed using the electronic engine management to disregard the accelerator input if the brake is used, an article in the New York Times mentioned that BMW, Audi and Volkswagen have already had this feature for a number of years.

    In the case of BMW, the accelerator is only disregarded if the brake pedal is pressed while car is moving, allowing the driver to race the engine for a racing-type start.

    Here is the article:
    http://wheels.blogs.nytimes.com/2009/10/07/smart-gas-pedals-may-solve-floor-mat-problem/?ref=automobiles

  • 2 FYI // Nov 4, 2009 at 11:40

    How could Toyota/Lexus not include this simple safety override into their “drive-by-wire” system (when the Germans certainly did…..)?! And how could any such system be officially approved and certified without it by any manufacturer?!

    October 7, 2000
    Smart Gas Pedals May Solve Floor-Mat Problem
    By Christopher Jensen
    http://wheels.blogs.nytimes.com/2009/10/07/smart-gas-pedals-may-solve-floor-mat-problem/
    (excerpts):
    Some automakers – primarily European — are using an unusual method to reduce the chances of unintended acceleration from something like a floor mat getting tangled up with the accelerator: smart gas pedals.

    If the vehicle is moving and both the gas and brake pedal are being pushed at the same time the computer tells the engine to ignore the gas pedal.

    “It is an additional safety feature,” said Thomas Plucinsky, a BMW spokesman. “The brake takes precedence.”

  • 3 Lynn // Nov 9, 2009 at 02:01

    I had 2 incidents in my 2000 Lexus GS 300 over the past 6 years. I took my car into the Lexus Service immediately after each time where my brake did not work and the car continued to accelerate. The first episode was at a stop light.
    There were no cars ahead of me. I leaned on my horn and prayed that the cars would stop for me as I ran the red light. I explained what happened to the service men at the dealer. They thoroughly checked out the car and found nothing wrong. The second time was at a stop sign where I slightly hit the car ahead of me as the brake did not engage. In both incidents my speed was under 20mph. I took the car in again to the Lexus dealer and once again they found nothing wrong nor did they give me instructions about putting the car in neutral if it should happen again.

  • 4 Joe Wein // Nov 10, 2009 at 08:17

    After the infamous “unintended acceleration” reports in 1986 (for which Audi was later vindicated) experts concluded that such cases were usually a consequence of a driver mistakenly stepping on the accelerator while intending to use the brakes. The more the car accelerates, the harder they push and vice versa.

    It was reported that imported cars (not just Audi) had both pedals closer together than US cars and the brake pedal was also smaller than in many US cars, making it easier to miss.

  • 5 FYI // Dec 25, 2009 at 10:00

    Toyota found to keep tight lid on potential safety problems
    http://www.latimes.com/business/la-fi-toyota-secrecy23-2009dec23,0,557792,full.story
    A Times investigation shows the world’s largest automaker has delayed recalls and attempted to blame human error in cases where owners claimed vehicle defects.

    NHTSA reviewing third generation Toyota Prius braking
    12/24/2009
    http://www.leftlanenews.com/nhtsa-reviewing-third-generation-toyota-prius-braking.html
    (excerpts):
    At least dozens of owners of the latest, third generation Toyota Prius have filed complaints with the National Highway Traffic Safety Administration in regards to alleged brake failures they’ve experienced. The complaints are centered around the transition from regenerative to traditional braking, and the possibility that extra force is required to properly slow the vehicle.

    When Toyota was approached by The Detroit Bureau about this matter they initially said they were unaware of the issue, but later released this statement, “We are aware of the complaints filed with NHTSA. The agency has not opened an investigation. We are investigating the issue based on internet traffic, customer comments to Toyota Customer Relations, and NHTSA complaints. It is too early to speculate the final conclusion(s) of our investigation and subsequent actions.”

  • 6 FYI // Jan 19, 2010 at 03:21

    ‘Toyota Avalon displays unintended acceleration without floor mat’
    By Mark Kleis 01/15/2010
    http://www.leftlanenews.com/toyota-avalon-displays-unintended-acceleration-without-floor-mat.html
    In a rather bizarre instance, a driver reportedly began to experience unintended acceleration from his Toyota Avalon and was able to drive the car to a nearby dealer with the vehicle still displaying wide open throttle, despite having the floormat removed. Dealer techs witnessed the problem and have reportedly offered to repair the vehicle free of charge.

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