Mitsubishi Montero mystery: The Case of the Sudden Unintended Acceleration (SUA)

First off, the definition of sudden unintended acceleration (SUA), from Wikipedia – is the unintended, unexpected, uncontrolled acceleration of a vehicle, often accompanied by an apparent loss of braking effectiveness. Such problems may be caused by driver error (e.g., pedal misapplication), mechanical or electrical problems, or some combination of these factors. Personally, I feel bad about Mitsubishi motors having to deal with this kind of issue in the midst of the release of their upcoming Monterosport. At the same time, I sympathize also to the victims of this seeming automotive malfunction.


I would just like to voice out my opinion on the matter. I am really surprised while watching some of the videos of the said cases that there are common denominators to all of them.

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  1. The vehicle emits black smoke before its acceleration be it forward or reverse. In diesel engines, this is an indication of overfueling, the same as suddenly stepping on the accelerator pedal full-on, meaning wide open throttle (WOT), pedal to the metal kind of thing.
  2. Brake lights not coming on before during and after the acceleration (usually their brake lights come on only after the accident). This can only mean one thing – the driver did not step on the brake pedals. Let me state as early as now that the brake lights in almost all vehicles are controlled by a switch directly on the brake pedal mechanism and does not involve any computer wizardry to make it light or to even apply the brakes.
  3. This happens only on the automatic transmission equipped car.


With the above points, I cannot help to deduct the following:

  1. Emission of black smoke can only happen when the accelerator pedal is suddenly depressed by the driver (unintended or intended). The case that the people who allege that there was a malfunction with the car’s system do not know the basics of drive by wire. This system deletes the need for a mechanical cable and has in its place the TPS (throttle position sensor). This is much like your volume control on your old transistor radio but more solid state (i.e., more resistant to dust, moisture, extreme temperatures). Its main purpose is to tell the (Engine Control Unit) ECU how far the driver has depressed the accelerator pedal. For this to go wrong the car would have been subjected to extreme conditions for a considerable amount of time and the most probable trouble after that would be no signal transmitted – or no more vroom vroom (loose contact). We can still argue that for some strange reason it has sent the wrong signals to the ECU but still we have:
  2. Brakes lights should come on instantly after a few millimetres of brake pedal action. This also gives signal to the ECU that the brake pedals have been depressed and the system should get ready to decelerate (i.e., ignition timing retards, fuel supply returns to idle volume, etc.) Even if, let’s say that, the ECU malfunctions and ignores the brake signals, even then you will not be losing any brake on any wheel and the brakes are conservatively designed to overcome the weight of the car plus much much much more, which only means that the car should stop anytime immediately. Brakes are one of the most heavily engineered parts of the car, and brake failure on a relatively new car would be the same chances as winning the lotto.
  3. It is quite evident on the videos, even though the drivers claim that they are experienced drivers, that they are not fully aware of driving an AT vehicle. One fact which supports this is the failure to step on the brakes while changing gears – very common mistake. This is evident in some of the videos because the brake lights did not light up in the instance that they are supposed to change gear, i.e. after driver change, coming from neutral, etc.

In conclusion, nobody would accept the fact that they mistakenly stepped on the accelerator instead of the brakes when you have just caused multi vehicle damages and/or death/injuries to pedestrians, especially with the Pinoys who are fond of “iwas pusoy”. And to the Pinoy driver, the “blame others” mentality trumps humility and all reason and logic. Instead of saying “I am sorry, I made a mistake”, the Pinoy would rather point to something else or someone for his predicament. Apparently, Pinoys find it hard to accept mistakes, especially when you have the opportunity to ride the SUA bandwagon. Add to that our low quality media sensationalizing the said incidents, they should not be feasting on it like houseflies on s__t without any conclusive information. The government for its part should have their mechanism set in place for similar incidents, all I see is a bunch of people who really do not know squat how and where to begin their “investigation”. They approved it being sold in the country, they should know how to handle this.

The case of SUA on the said maker/model is also highly suspicious as only vehicles in the Philippines suffers from it while all Monterosport  supplied to other countries are also made in the same plant in Thailand. Moreover, car makers would be using similar parts to other makes and models, why are there no cases of SUA for those models then? And if drive by wire was so unreliable why is it so widely used for decades now not only in the car industry? All other big name car manufacturers are using the same drive by wire system which only proves that this system is reliable and safe.

[Photo courtesy]

19 Replies to “Mitsubishi Montero mystery: The Case of the Sudden Unintended Acceleration (SUA)”

  1. there was an article in the inquirer which made several points, here are 2 of them

    Another vehicle a pickup (I think its the L200???) shares the same front end including the throttle and brake mechanism)as the montero. But there are no SUA problems for the L200.

    The monteros in the philippines are imported from thailand and thailand also supplies other countries with the exact same models but nowhere is the SUA problem as bad as in the philippines.

    Both are kind of puzzling if it really was a factory defect.

    If we had indipendent confirmation that the brake light really is a simple switch that functions even if the car’s computer is not working then that’s more evidence

    I really believe we should have indipendent experts so that the question can be solved.

  2. To reply to a certain EJ Mangahis on the electronic book of faces as I do not have any facebook account, even though I would rather he focus on the matter at hand rather than expound on my qualifications:

    EJ Mangahis said “I think the writer is not even a mechanical engineer with automotive units., if u own a montorro the toro and havent experience SUA u’r damn lucky, and auto transmission is the easiest thing to drive ..couple of days ago HONDA recalled some jazz units to replace the Elect systems because of a stress raiser issue on its drive shaft..they didnt wait for an accident to happen they prevented it to save their brand maybe mmpc should do the same”.

    Let me indulge him. Yes I am a mechanical engineer by profession. I have worked for the auto industry as a product development engineer for 7 years, before going to a more lucrative engineering discipline. I am also an avid auto enthusiast not only into driving but by caressing each and every small part of the car. So there….

    If there were any cause for recall then the car maker would have done that already. FYI car parts are also made by 3rd party companies who usually also supply other car makers. Did you think that the electronic components for your car is made in house by the same car maker? My point is, it would be easy for the car maker to sue his suppler for damages if it is so warranted.

    Electrical system…… then you say stress raiser……then you say drive shaft….hmmmmm something is out of place there, my friend.

    Lets get back to the topic though, using the argument that I haven’t driven one with SUA so that makes me unqualified is so so ……. failed argument.

  3. Mitsubishi is allergic to recalling its products. Nobody mentions the scandal Mitsubishi was involved in when it covered up the defects of its vehicles in Japan back in 2000 and 2004. It’s the main reason why the brand lost its luster in several markets.

  4. Car now are electronically controled and computer controlled. There is a computer Integrated Circuit, that controls the car. Maybe, there is a “Bug” in the Computer Program of the Integrated Circuit.

    This Itegrated Circuit controls, the :Acceleration, Brake System, Fuel Feed System, etc…

    In Detroit, Michigan, U.S.A.; they have the Prototype of “Driverless Car”…You just sit , at the back of the car. You put, your destination in the Global Positioning System (GPS). The car will take you to your destination.

    I am still afraid of these kinds of cars. Computer Programming is not yet an exact Science. It is very hard to Debug, all of the computer programs. Some companies, just sell these cars, to countries, that have questionable judicial systems. They know, they can get away with it, if accidents happen, because of their idiotic need for more profits. And, beat the Deadline of the release of New yearly models of their brand.

    1. err… as if these cars you talked about (i.e. google car, tesla, nissan leaf) are that affordable just to be sold to countries that have questionable judicial systems for profit.

      1. In the U.S., Mitsubishi would had been subjected to multi million dollars lawsuits. There are Technical people, who can do good investigations, what went wrong with such models of defective cars.

        The latest scandal was the Volkswagen Company, inserted a computer program , in the emission tests of the Volkswagen models cars; to pass the emission test of Volkswagen cars. The sales of the company went down, due to this cheating.

        General Motors car models, have steering wheel problems, a few years ago. The company(General Motors Corp.) , was forced to repair all the ignition key system of such defective cars.

        Ford Motor Corp. had also problems, with the inflation of an airbag system, in their cars. Airbags were made by a Japanese manufacturer. So, Ford Motors Corp., was ordered to replace the airbag system, in their defective cars.

        People killed caused by these accidents due to these defective cars, were awarded monetary compensation by the U.S. courts.

    2. The ECU does not control the car. It only manages the engine as required by the driver. The car as a whole is still controlled by the driver himself.

      The engine control unit (ECU) of a car only manages the engine. Brakes or all on their own and just need to feed information to the ECU for the corresponding engine response, i.e. fuel volume goes back to idle quantity, ignition timing retards, etc, when the brake pedal is depressed. There is a very slim chance of a “bug” for this major car component as it has gone through years of research and rigorous testing before it can be approved for production. To add to this, automotive engineers have put in “fail safe” features just for the remote possibility that anything goes wrong with the ECU. The ECU should exceed even the lifetime of the car and would only require replacement if the ECU was exposed to abnormal situations i.e, car was flooded, improperly tinkered upon by tuners.

      I do share your fears with the driverless cars though. Taking the human factor out of the equation just doesnt feel right.

      1. Sudden acceleration has been a problem, also in other car models. A thorough investigation by capable Technical People should be done. I still believe, that there is something wrong with the computerized Integrated Circuits in the car model. The Integrated Circuits, affect directly/indirectly to the performances of the model cars, including this sudden acceleration phenomena.

        1. @HT

          Numerous studies and research has been done regarding SUA(not exclusive to one car maker), to the point of trying to replicate the theories that the researchers have introduced. But nothing conclusive came out of it. Here is one link:

          but still mentioned at the end that more research is needed to conclude his theories.

          Jon is right in saying to not take the human factor out of the equation. After all, these are just machines, which all use the same logic – garbage in, garbage out.

          Even if the above theory from autosafety is proven to be right, there is nothing to prevent the driver from stepping on the brake pedal ( the stop pedal, the right one, on the left, usually larger to accommodate two feet stepping on it) and ultimately stopping the car.

  5. i encountered similar scary SUA to my old Kia 02 sportage automatic…but that’s probably due to wear & tear..of.. the TPS (3-connector).since i could not find exact replacement…i have my ignition pump (filled w/ 3-4 electronicky type sensors!) replaced w/ surplus non-electronicky ignition pump

    Thus i reverted to age-old reliable accelerate-by-direct cable to pump from accelerate-by-wire.

      1. @JOn:

        Human errors are possible. However, there are Technical People, who understand the problem of Sudden Acceleration on car models. It is nothing new…

  6. This Sudden Acceleration problem on new models of cars had been solved by car designers/makers in the U.S. You can see their Technical Report, thru Freedom of Information(FOI). I don’t know , if the American FOI, is applicable outside the U.S.

    This car design problem is nothing new.

  7. It was like being in a car with the gas pedal slammed down to the floor and nothing to do but hold on and pretend to have some semblance of control. But control was something I’d lost a long time ago.

  8. I have a Mitsubishi L200 Warrior with automatic transmission and selectronic 4×4. Sudden acceleration has occurred twice in four year and terrified me both times. The first time Mitsubishi investiagted and I replaced the accelerator pedal. The second time was four years later at a junction. Both times no injuries and I was able to slow the truck with the brakes when the accelerator reset and gave no more trouble. I still drive with my left foot hovering over the gas pedal. Both cases were investigated by expert mechanics who could find no fault. Something is wrong – a bad line of code or other very intermittent fault. I honestly don’t know what to do but have refrained from selling the truck as I would not wish to pass this problem onto somebody who would be unaware of the dangers.

  9. The videos showed this Diesel Montero’s emits a heavy black smoke everytime it gets itself out of control. Most of the videos showed the unit emitting a black smoke after it bang itself around, some of the videos emits a heavy smoke before its start banging out of control. True to this statement, a heavy black smoke means that the diesel mixture is on rich fuel state. It somehow theorized that the engine builds-up inside it then a sudden release, the tranny is not mechanically controlled but electronically since the monty is an invecs tranny technology, it may be triggering the the wrong solenoid. Also i saw a analysis that among SUA cases bearing design flaws on the suction control valve of the fuel. The common reverse to forward motion of the vehicle is yet another mystery it can only happen if the solenoid been triggered fuzz from the fuel build up.

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