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Old 09-26-2011, 04:32 PM   #1 (permalink)
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Unintended Acceleration ?

Mrs A complained about the number of rattles in her Prius and demanded action - actually she parked it in front of my Aygo and "suggested" I take A Junior to his cub scouts and spend some time with the Prius to remove rattles. Usually Mrs A won't let me drive the Prius, maybe in case I get better FE.

So I reset trip meter B and dropped off A junior at cub scouts and went rattle hunting. Most were simple - the boot (aka Trunk) tray not fitting properly, stuff in the tray and stuff in the door and the centre console bits and pieces. There is one under the front dash behind the steering wheel which I think will need the local Toyota dealer to investigate, but it is hard to recreate. The boot tray is a cr@p fit, so it rattles a lot.

So given that this was my first chance to "play" with our Prius I tried the Hybrid system. I worked out the method of fooling it into switching the engine off at 30-35 and then cruising at 30 on city streets. I worked out how to get the thing to cruise at 65-75 easily and even worked out a method of using EV mode to get the thing to 35 with no IC and then switch to Eco mode to hold it there.

I got an average of 76 MPG (imp) on trip B, and was happy to suggest that 80-90 would be possible with some effort.

On two occasions though the Prius did "go" when I didn't want it to.

Both times I had parked up and then just set off, pulled out of the car park and then acclerated hard to get up to 30-35 before I could ease off and get it to turn the engine off.

Except when I lifted off, the pedal stayed down and the car continued to gain speed. I pushed hard on the pedal the first time and it popped up, the car regained control. I pulled over and checked for obstructions - mats etc. but there wasn't any - we do have some on order for winter.

The car behaved until I parked again and then shortly after I set off and repeated the acceleration / lift-off operation the car continued to accelerate again. Pushing and releasing the throttle pedal freed it up again.

I checked whether the cruise was on and maybe I had set it but it was off - I turned it on and off without setting it and it didn't kick in.

Any ideas ?

Mrs A has not reported any out of control moments but TBH roads in Scotland are useless for cruise control so we don't use it much. For the next few days I have child duties - taking A Junior to school and then picking him up for after school activities, so he will be in my Aygo instead.

I'm worried about it though when he gets back in. But probably like a lot of drivers I wonder about what happened.

I do know EM has looked at the Toyota Acceleration issue the evidence seems to assumed driver error but this was definitely not. I'm not a big user of autos but I'm sure it wasn't me.

Anyone else, advice ?

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Old 09-26-2011, 04:54 PM   #2 (permalink)
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I'm not a big user of autos but I'm sure it wasn't me.

Anyone else, advice ?


your a power hungry,
"i can drive better than my wife',
unappreciative,
heavy footed,
in denial,
frustrated
Englishman
living in Scotland...........

ok...........

Now about the unintended acceleration............




dammit........were are my MEDS?????????>>?>?
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Old 09-26-2011, 09:04 PM   #3 (permalink)
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@Arragonis- That's some pretty serious sh!t in my opinion.
Can you take it to your dealer and tell them about it?
I work at GM dealer and we are still getting in some Pontiac Vibes(=Toyota Matrix) for the recall to cut the gas pedal down and remove a piece of foam from the area under the carpet.
These new cars with the every driver input is just a request to a module that's going to talk to other modules and decide what to do is making me feel much safer in my 500 $ piece of crap where I can do a number of things in an emergency.
I mean if that thing decides to go WOT there isn't even a key to physically cut ignition power if I'm correct. You have a push button right? That's another request to probably the same ECU that just went nuts. (if that's the case)

Sorry I do not mean to sound so alarming,I know most new cars are this way and when throttle related sensor data goes out of range for the ECU they are setup to go into reduced engine power (GM does) basically throttle goes to idle and no input accepted until code cleared or next ignition cycle does not see the fault anymore but what you experienced has to be investigated.

Sorry, me as a mechanic seeing the direction the new vehicles taken pisses me off because I have to deal with the out of control ultra sophisticated garbage on many levels. And instead of them working on reliability....I'm going to shut up now.
I apologize for the rant again but please have that thing checked out and if this symptom is not familiar to them at your dealer,I would suggest they make a report to Toyota technical assistance center or what ever Toyota has and let them know about it!
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Old 09-26-2011, 09:33 PM   #4 (permalink)
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Quote:
Originally Posted by Arragonis View Post
. . .
Except when I lifted off, the pedal stayed down and the car continued to gain speed. I pushed hard on the pedal the first time and it popped up, the car regained control. I pulled over and checked for obstructions - mats etc. but there wasn't any - we do have some on order for winter.

The car behaved until I parked again and then shortly after I set off and repeated the acceleration / lift-off operation the car continued to accelerate again. Pushing and releasing the throttle pedal freed it up again.
. . .
Any ideas ?
Your symptom, the pedal physically remaining down, is consistent with some interference. Here in the USA, we had a recall of accelerators in the NHW20 because of poor quality of the accelerator assembly. The fix was to put in a 'shim' and I remember something about trimming the accelerator.

First, I would recommend seeing if you can replicate the problem at will and then demonstrating it to your local Toyota dealer. But do treat it as a serious issue.

The accelerator assembly has no external, mechanical connections. Whatever is bad is within the assembly. So try pushing the accelerator (car off) and rotate the center of pressure in a circular pattern. Of course, try to use the same shoes but don't be afraid to take the shoe off and use a stocking or bare foot to feel for any binding.

What about the weather at the time? In particular temperature and humidity.

Are there an 'unusual' soil, dust or dirt in your area?

Had the car been in use before the 'sticky pedal' or was this after some "n" estimated minutes or miles?

This is the 1.8L Prius? The reason I ask is I've bought a used, NHW20 accelerator assembly but haven't taken it apart, yet.

Thanks,
Bob Wilson
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Old 09-26-2011, 09:52 PM   #5 (permalink)
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You're right Bob! IF the pedal truly stuck it can not be anything else but the accelerator pedal assembly itself. (he said no floormat interference).

But what if the brain associated the takeoff with the pedal down and really the pedal was never stuck? I'm not doubting what he felt,just suggesting the idea.

Tie a rope to that sucker and next time it happens pull on the rope to see if it's the pedal?

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Old 09-26-2011, 10:18 PM   #6 (permalink)
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Arragonis -

I would read this thread :

http://ecomodder.com/forum/showthrea...all-12112.html

Then I would try to find out if your pedal is the same *design* as the one made by CTS Corporation. If it is, then I would try to replace it with the one made by Denso, which is a different design :

Quote:
Originally Posted by Daox View Post
Good analysis of both pedals by a third party (impartial AFAIK). They took apart both and reviewed the flaws in the CTS pedal.

Why Toyota Must Replace Flawed CTS Gas Pedal With Superior Denso Pedal | The Truth About Cars
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Old 09-27-2011, 04:40 AM   #7 (permalink)
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Thanks for the replies, even Mcrews who raises a titter

@CFG - Thanks for the link, I read that and it states the 2010 Prius (ours is a 2011 1.8L T-Spirit) is unaffected. I haven't read it all yet though, I will before we go into the dealer and maybe print some bits off.

@3dPlane & bwilson - It will be going to the dealer asap but I'm not sure I can get it to repeat on demand. There isn't anything unusual I can think about in our area - no especially heavy rain or unusual temps or dirt etc. Our area is typical UK "green and pleasant land" if you know what I mean and the car lives on tarmac and solid ground - no dirt or grass.

@all I checked with Mrs A this morning and she hasn't had it happen to her at all and thinks I need new pills - or is convinced I activated cruise by mistake which I'm sure I didn't - no speedo with the arrow symbol light on the dash.

Could it be the technique I was using ? I had it in Eco mode and was accelerating firmly but not dragster style to the PSL (30) and then lifting off so that the Hybrid system shut off the engine and we would coast. When I lifted the pedal didn't come up so its more a physical thing, although cruise does hold the pedal position? I did this probably 50-100 times during my couple of hours drive and it only happened twice. The pedal hasn't been sticky or stiff, but I do find it stiffer than my Aygo's which is a traditional cable type.

The only correlating factor could be that up until this point before both events I had been parked and then had been travelling slow enough to be running on battery only up to the point I accelerated so this was the first engine start since I had turned the car on again. But again I had stopped 4 or 5 times previously on rattle hunt and it didn't occurr then.

I'll report back what the stealer says when it gets in, this PM.
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Old 09-27-2011, 07:44 AM   #8 (permalink)
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Quote:"When I lifted the pedal didn't come up so its more a physical thing, although cruise does hold the pedal position? "

That is the key! No,cruise does not hold pedal position! Like Bob said earlier nothing mechanical is connected to the pedal! (and it does not have an actuator built in it!) So IF the pedal really stayed down then it can ONLY be the pedal assembly!

Your best chance at being taken seriously at the dealer if you would type up the circumstances at the time it happened with as much detail as possible and hand it to them and make sure the tech who works on it gets it so they can attempt to duplicate it!!! I am a "stealership" tech and when I get insufficient information on something intermittent, I will not waste much time on trying to duplicate it unless I think I have a good chance to reproduce the complaint.
(we don't get paid for driving around!!!)

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Old 09-27-2011, 08:39 AM   #9 (permalink)
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So the accelerator is pretty much a pedal, a pot and a wire?
When you push on the pedal, a pot is being turned, and the position is used as the signal..

You aren't in control of that car, it's just seeing you as one of many inputs to it's system.
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Old 09-27-2011, 08:51 AM   #10 (permalink)
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@3d - I think that may be the issue - i.e. if its not reproducable they probably won't try to. However its a lease (employer supplied) car so if nothing else fails we get them to take it back.

@toc - thats the same in most cars nowadays - I think the old fashioned cable in my Aygo is still just connected to the ECU.

In a key operated car of course you can turn the key. What do I do if the Prius ignores the off button ? I know - hold it in for 6 seconds - works in PCs

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