Anyone Tried These Tests On Their Car(s)?

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  #1  
Old 03-25-10, 10:49 AM
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Anyone Tried These Tests On Their Car(s)?

First Test:

I have two cars that have the drive by wire system. I was wondering what happens when I put my foot on both the accelerater and brake simultaneously.

The test is simple to administer. Drive the car on the highway clear of traffic and accelerate the vehicle with your right foot on the throttle. Then with your left foot lightly press the brake pedal and see what happens.

One of my vehicles, an Acura, will continue accelerating. I have warned my wife about this and actually had her try it to demonstrate. The other vehicle, a Mercedes, immediately goes to idle when the brake is pressed when the car is in motion.

Second Test:

This one applies to any normally aspirated gasoline powered vehicle. Floor the accelerator and start rapidly pumping the brake pedal. Unless the vehicle has the throttle disengage software as noted above, you will quickly run out of vacuum and your brakes will no longer work properly. At full throttle a gasoline engine will not build vacuum because the pressure in the intake runners is essentially atmospheric. I first noticed this back in the early 1980's with a Bowden cable type accelerater linkage. Brake pumping at full throttle would not prevent the car from accelerating. This is something to keep in the back of your mind just in case a throttle, for any reason, ever gets stuck wide open. In that situation it would behoove the driver to use the brake once and firmly.

Diesels operate differently and generally have a vacuum pump to maintain vacuum for brakes, etc.....at least the one I owned worked that way.
 
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  #2  
Old 03-25-10, 11:47 PM
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After the Prius that ran amok supposibly on that guy I had a cust request that I "test drive " theirs to see what would happen.
Full throttle light braking the car continued to accelerate.
Full throttle hard braking it took aprox. 15 to 20 secs before the car did the same as your MB.(Drive disengaged and went to idle) Personaly I feel thats too long but its the way the cars software seems to work.
Also tried to shut it down by pressing the power button(Gen 3 Prius) car did not shut down till under 30 mph.However with the hard brake to disengage the drive not really a problem to me.I'd want the engine still running anyhow till that point to assure the computers were still powered up the ps is elect. power assist same with the brake system the only direct connection the driver has is the steering all else is drive by wire. My Personal view on this is more toward the side of driver error than auto issues.But not totally willing not to believe there may be a programming issue involved as well.
Going to a 3 day Prius Class next month where we will be totaly dismantling the drive train and learning all the ins and outs of those autos.
 
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Old 03-26-10, 06:42 AM
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Great information.

I would like to add if you have a stuck accelerator, put the car in neutral. You can do this with any automatic or manual transmission.
 
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Old 03-26-10, 03:51 PM
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That is one of the programming issues I feel needs addressed by yoda your shift selector on gen 2 and later is nothing but a glorified computer joy stick you can try and put it in neutral all you want and the car "thinks" your an idiot and ignores you if under power (driving) at the time, there is a process that takes about 10 min to perform to put it in neutral so you can align the blankin thing LOL.Forgot this in my other post sorry all.Also get this if the key fob is close enough to the car it will start and continue to operate without being in the car! LOL Try that one for forgetting your keys.I had the key fob on my aligners control box (aprox 2 feet from the car) and the thing still started up and drove before I realized where I left them. Modern tech. ain't it great?! LOL
 
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Old 03-26-10, 04:08 PM
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The more I read these posts the more I want a 1970 or earlier Chevy with a 250 engine and a single barrel carb.
 
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Old 03-26-10, 05:22 PM
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Originally Posted by ray2047 View Post
The more I read these posts the more I want a 1970 or earlier Chevy with a 250 engine and a single barrel carb.
Yeah! I am absolutely intrigued reading these threads that say you can't shut off the key without consequences, or braking is lost with no power or otherwise ineffective with uncontrolled acceleration, and putting in neutral don't help(or not right away),etc. Like you are trapped without a way out. How did the engineers miss this? Or DIDN'T they, and someone is failing to explain something or something right, here?
 
  #7  
Old 03-26-10, 06:04 PM
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??????????????------

A few Isolated incidents and the whole country goes MAD???????

First off......There is not a car "alive" with a vacuum assist brake system that can stop an accelerating vehicle, regardless of whether the accelerator stuck, or you pound gas and brake at the same time to see what happens. Ultimately, you will either wreck the car, or tear the motor mounts out of it.

Now.....Drive-By - Wire..for the purpose of discussion..Basically consists of 2 rheostats. One counts from 0 to 100, the other counts from 100 to 0. 0-15 and 100 to 85 are not used, so if the computer sees a reading below 15 , or over 85 it will default and close. the rest of the process is a percentage calculation between the two.If sensor 1 says 20, then sensor two will say 80, which would be 5% throttle. There is a max of 2 percent variation before the PCM defaults to closed throttle. In a perfect world, it is "Impossible" for a Drive by wire system to run away uncontrolled.

Now , I work for Chrysler, and since the Auto industry is in financial "Shambles", I have no choice but to DESPISE Toyota. Everyone that does NOT buy a Toyota, allows me the opportunity to make a living. Having said that, The few reported incidents, regardless of the accusations against Toyota and how they have handled the Legal end of things,Have led to the "LESS ETHICAL " amoung us to "Milk the Gravy Train".

Blaming uncontrolled acceleration to get out of a speeding ticket (Gently pumping the brake and gas so the Police officer behind you with Lights and sirens is sure to see your brake lamps) To documenting a problem with your dealership, so in two years when you wreck your car, you can blame someone else. Over the past month or so, Ive had several customers complain of uncontrolled accell and the inability to stop. Not ONE has been verified. My personal favorite is the guy with 35900 on the odometer, who has been in once a week complaining of this. Well, today he was in, and, his Durango turned 36,000, the warranty is over, so he was told there would be a Diagnostic charge.....He promptly walked out......
Issues arise all the time, so let the engineers fix their mistakes, and stop panicking......
 
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Old 03-26-10, 06:16 PM
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Copy that ecman my first car was a 58 Impala 348 w 3 duece carbs.I still have about 12 yrs till I retire and think this is the way all autos are going.It's good in some ways but the programming still has some bugs in my op. I have had to spend more time in classes than the average doctor did to keep up with the changes and it's speeding up every year anymore.The average person has no idea how much computer control there is in some of these autos and their just along for the ride to point it in the direction they want to go.
 
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Old 03-26-10, 07:51 PM
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These are some of the most intelligent comments I have read on the entire Toyota media extravaganza. I know this company and know that they are anything but irresponsible when it comes to their vehicle safety and quality. I also believe when it is all yesterday's news the truth will be that there were a couple of cases of wrong floor mats jamming the accelerator pedals, and perhaps 3 or 4 cases of slow pedal control return. The massive recall response was all about politics, and media pressure. Didn't Ford have around 300 complaints about acceleration up until last September. Unclediezel is correct on all his points as far as I am concerned. Now is probably a great time to buy a Toyota or Lexus product for anyone wanting one. The price has never been better. Most of them have more North American work content in them than Chevy Impalas have these days after GM went on their massive Chinese parts buying spree a few years ago. I worked for GM at that time and saw it all happen. It is too bad that long gone are the days that Maniac is talking about when an Impala was an Impala. Real Delco Remy, or maybe Rochester American made parts, a shade tree and a tune up kit. I had a '58 once also but by the time I got it, I left a little bit of the Fisher body at every turn due to rust, but what a great car it was to drive and work on.
 
  #10  
Old 03-27-10, 05:53 AM
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Originally Posted by Unclediezel View Post
??????????????------
First off......There is not a car "alive" with a vacuum assist brake system that can stop an accelerating vehicle, regardless of whether the accelerator stuck, or you pound gas and brake at the same time to see what happens. Ultimately, you will either wreck the car, or tear the motor mounts out of it.

....
Are you sure you typed what you intended to say? Brakes on any passenger vehicle will overcome the engine if pressed once. Car and Driver did a test a couple of months ago. They drove a number cars at 80 mph, floored it, and pressed the brake pedal once. Every one of them stopped except a Roush Mustang with over 500 hp. It slowed to 15 mph but that is all. I've tried it with every car I've ever owned and every on of them stopped with a single hard application of the brake.

Secondly, the forces on the motor mounts are the same whether the brakes are on or not. It is only dependent on motor torque output.

From what I've observed over my 15 years as a driving instuctor for a number of sports car clubs is that factory brakes will stop you very well. The repeatability (ie laps on a road course racing circuit) is where the trouble starts. With many cars the pads have to be changed to higher performance pads or brakes have to be ducted to reject heat faster or the calipers, rotors, and pads all have to be increased in size.
 
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Old 03-27-10, 05:56 AM
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Just adding fuel to the fire. Have you heard the latest? Now the elite are saying the uncontrolled acceleration was caused by the car passing under high voltage distribution lines during acceleration. Hey, it causes cows to give less milk, so it is probable THE answer we have been looking for.
 
  #12  
Old 03-27-10, 06:09 AM
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I imagine some drivers are at fault or they are trying to work the system.

But what makes me wonder about software or interference is the state trooper incident in the Lexus rental. I suspect the trooper knew what he was doing yet the car got away from him. Gotta wonder....
 
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Old 03-27-10, 03:44 PM
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Lawrence,

Why wasn't that Lexus able to stop, that ended up crashing and killing all the occupants, while the 911 operator was on the line?
 
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Old 03-27-10, 06:29 PM
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MY 91 OLDS has power brakes so if i loose the engine i have no brakes(also had a brake line snap but even though all fluid blead off somehow the car still stopped even though i was going like 10PMPH all the way home pumping the breaks) found this out the day i got the car. the people i got it from sold it to me with a tank full of fumes(at least they gave me a empty 1 gallion gas can) made it 1 mile to the gas station car dies in the middle of the road car coasts. had to run to the station and put one gallon in the car then pull it into the gas station. cost me $50 worth of gas. how much damage would accure if say your going 60MPH on the freeway engine goes no brakes and you shove it into PARK would it rip the car in 2.
 
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Old 03-27-10, 07:04 PM
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Lawrence...

While I do agree with how you responded, what I intended to get across was based on the General publics knowledge of brakes. If a car stops at 60 to 0 in 200 feet, and the car that is stopped in front of you is 198 feet away....Plain and simple.....It didnt stop... Couple this with the lack of vacuum at Full throttle, and the inevitable brake fade from standing on the brakes, and to the 17 year old girl who just got her liscense 3 hours earlier..... you have a car that Doesnt stop. That same car that brakes from 60 to 0 in 200 feet, is Never going to come to a complete stop in 200 feet with a fully torquing engine forcing against it. The problem arises when the "Immovable Object" is closer than your "Corrected projected stopping distance".... As far as motor mounts tearing out.... Back in the day , you stabbed the brakes as hard as you could , and then mashed on the gas....The rear wheels lit up like a Xmas tree. But until the tires lost their bite, the mounts were stretched about as far as possible. If the engine didnt have enough "PUNCH", the car may have "Crept " a few feet. Instantly, some one would point out that your brakes werent holding back the car. Not to "Stab" at anyone...But the greatest technology ever created, is wasted on those who dont understand it, or worse, those who dont know what it is supposed to , or not supposed to do.
On a Lighter note, to answer your original question, While I didnt actually get to try it, A 2009 Chrysler 300, does have a Brake switch input Bussed to the Throttle control module...Other than altering throttle control during brake application....I dont know why else it would be there.....(Mother Mopar has "Triple assured "us that Uncontrolled accelleration CANNOT .....Repeat...CANNOT HAPPEN....)
 
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Old 03-27-10, 07:33 PM
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Just really quick......Chandler.....All jokes aside.....
Years ago, We had a customer with a 1990 buick electra ,That complained of a check engine light flashing momentarily every time she would pass a Specific intersection. For months we thought she was crazy, her husband thought she was crazy, Until she drove me passed this specific intersection, and I saw it for myself. At the northeast corner of the intersection was a NYC transit Radio Tower.... I do realize this is a "ONE-OFF" freak, but there have been rumors of cellphones creating Havoc with hospital equipment, and Air Traffic, So why is that so far fetched?????
 
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Old 03-27-10, 07:42 PM
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I have been out of professional wrenching for 18yrs. but the last time I really checked all of the vehicle tested had brake systems that would overcome the engine when properly applied, that being said most people panic and don't use any sense when something outside of their experience happens. case in point engine dies on highway you are in the left lane 9 times out of 10 the driver instead of signaling and moving to the right out of traffic to stop they will immediately hit their brakes and pull into the center median thus becoming a traffic hazard.

murphy was an optimist
 
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Old 03-27-10, 07:48 PM
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Originally Posted by Unclediezel View Post
Just really quick......Chandler.....All jokes aside.....
Years ago, We had a customer with a 1990 buick electra ,That complained of a check engine light flashing momentarily every time she would pass a Specific intersection. For months we thought she was crazy, her husband thought she was crazy, Until she drove me passed this specific intersection, and I saw it for myself. At the northeast corner of the intersection was a NYC transit Radio Tower.... I do realize this is a "ONE-OFF" freak, but there have been rumors of cellphones creating Havoc with hospital equipment, and Air Traffic, So why is that so far fetched?????
I had a '90 Dodge P/U that I installed a CB radio in. Sometimes but not all the time, when you keyed the CB mic it would make the windshield wipers turn on.
My question is: If an automatic trans equipped car does have a full throttle runaway, if you can brake it down slow enough to make it shift into 1st gear, I doubt you'd be able to bring it to a full stop since the brakes would be extremely hot by that time. Hopefully the speed would be slow enough you could run into something w/o a fatality causing impact. I personally think they have a bunch of dumba$$ Geeks that program a computer that won't let the driver put the trans in neutral at any speed.

Mike
 
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Old 03-27-10, 08:11 PM
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Agreed......Brakes ...like all other systems are engineered to function thru a wide range of situations....

But to a new or inexperienced driver, or a seasoned veteran in a Time of "PANIC" The systems do not respond the same in ALL situations. Think of a feeble old 80 year old woman in her 1970 Cadillac when a power steering hose breaks.....Yes the car will still steer, but without power assist.....She will Not be able to steer it. In her mind...she lost the ability to steer the car.....

A vacuum assisted brake system has little to no "Supply" vacuum under Wide open throttle conditions. That ...In and of itself is a NORMAL charachteristic of the internal combustion engine.
Will the car stop ....Yes ..absolutely....will it stop in the same amount of distance, or at the same rate of deceleration??????? Was there sufficient "Time and Distance" to allow the "Handicapped" system to do its job???? In the mind of Joe Q.Driver, his car didnt Stop. Three times the Normal stopping distance Isnt enough, when you barely had enough to stop the car under normal conditions.
 
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Old 03-28-10, 09:22 AM
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Originally Posted by Speedwrench View Post
..... most people panic and don't use any sense when something outside of their experience happens.
But wouldn't trying to brake a car that keeps going faster, be an instinctive reaction? If it is NOT, I guess people better start trying to keep that thought in the back of their mind then.

The same(instinct) as if say you you are losing control of a car on snow - you instinctively correct the wheel the way you want the car to go in?
 
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Old 03-28-10, 09:28 AM
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Unclediezel,

Glad to see you are back. We need you here. [Hopefully your sewer(was it?) does not act up and.......]
 
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Old 03-28-10, 08:35 PM
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i ask again if you use up the brakes and the car is still speeding up what happens if you slam it into park supposing you could get it to shift into park or shove it into reverse.
 
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Old 03-28-10, 09:14 PM
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You would probably 'use up' as you call it, the front brakes well before the rear considering that the front generally do 60 - 70% of the braking. In this hypothetical situation a front drive vehicle obviously would continue to pull against brake locked rear wheels, while a rear wheel drive should respond to an activated parking brake even if pulled on as a last resort. On the other question, assuming that there is a parking pawl inside the transmission, even if you could select the Park mode, the pawl would simply break. Parking pawls when used can break at even a very slow roll situation never mind at faster speeds. In regards to attempting to shift a rolling car into reverse, modern cars with computers have software that would simply ignore such a command just as they ignore commands to shift to 1st gear at 40mph. Most expert articles that I have read are in agreement that in the very unlikely event a vehicle with an auto transmission did experience rapid acceleration not generated by a drivers response, the best thing to do before trying anything else is to immediately jump on the brakes with both feet, and hold them under heavy pressure while you play with gear shift selectors and off positions on keys, or electronic buttons. I think there is also some truth from those that have written recent articles that as vehicles have become easier to drive with technology now all over the place, drivers have become perhaps either less skilled, or at the very least less attentive, and subsequently slower to react to immediate dangers, or when they do react, do not react in the correct way. As fast as car safety has improved over the years, the driver remains the most dangerous part of a car.
 
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Old 03-29-10, 09:03 AM
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Originally Posted by flirty1 View Post
i ask again if you use up the brakes and the car is still speeding up what happens if you slam it into park supposing you could get it to shift into park or shove it into reverse.
I have lost all brakes in cars or trucks and out of panic threw the lever into Park - and all I got out of the deal was a ratcheting sound. Yet, nothing (the pawl?) broke. It still allowed the car to stay in Park after the car was stopped(by ditching the vehicle into small trees or snow banks). At least that was the case with my 70-ish vehicles.
 
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