Car Seems To Accelerate By Itself

[miss_d_bus]

I have a 07 reg automatic Aygo + 3dr.

Recently I have been having this strange feeling that my car accelerates a little by itself at low speeds. I thought it might just be the shoes I'm wearing and how near I am sititng to the steering wheel and thinking it was just being a bit heavy footed but I am not so sure now. I don't notice the problem at speed but I have noticed it whilst in traffic. It sometimes feels like the car is speeding up by itself and a bit jolty when it does it. Now you might think its because I am going down a hill, but I was going down a flat road that had loads of speed bumps so was slowed right down for them as they are the highest speed bumps I have ever seen and when I got over the bumps, the car sped up without using the accelerator up to 30. I wanted to see how fast it would go by iself but its been hard to test because of other motorists about/speed limits. It doesn't happen all the time either.

Part of me is thinking its in my head but I have been regularly driving this car since September 2007 and this now seems out of character.

Any ideas of what this could be ?

I feel a bit relucant to take it to the garage until I'm totally sure its the car and not my imagination....

Thanks,

Catherine

[Jan van de Wouw]

If you have an automatic you've got Throttle-By-Wire: you tell the car you want

to go faster and the computers and actuators take the actions needed to do so.

So there is no direct relation to your throttle pedal and the actual throttle body:

the car CAN speed up, then shift up, let go of the gas and doddle on at a lower

revvcount all on the same Throttle Position...

If this only occurs at lower speeds it might be that you're going slow

enough for the computer to "doubt" which gear to select and is

speeding up to shift up of revvs the engine to keep it from stalling...

You have to keep in mind that the "automatic" is actually a manual box that's

computer-controlled, so the car responds WAY different than a conventional

automatic with planetary gears and a torque converter would...

[miss_d_bus]

If you have an automatic you've got Throttle-By-Wire: you tell the car you want

to go faster and the computers and actuators take the actions needed to do so.

So there is no direct relation to your throttle pedal and the actual throttle body:

the car CAN speed up, then shift up, let go of the gas and doddle on at a lower

revvcount all on the same Throttle Position...

If this only occurs at lower speeds it might be that you're going slow

enough for the computer to "doubt" which gear to select and is

speeding up to shift up of revvs the engine to keep it from stalling...

You have to keep in mind that the "automatic" is actually a manual box that's

computer-controlled, so the car responds WAY different than a conventional

automatic with planetary gears and a torque converter would...

Thank you for clarifying the technical side of it. I realised it was basically a manual gearbox with a computer controlling it but my understanding was literally just that so you've brought it into context for me. I'll just have to see how it goes over the next 6 months before the warranty runs out to prove whether it is just as you describe or something a bit sinister. It might just be I've not noticed it doing it before as usually I've found the opposite to be true; the car can be sluggish in low gears. Its quite annoying that the UK driving test doesn't prepare anyone to drive such cars and I learnt with a CVT gearbox and was shocked the first time my Aygo started to roll back on a small incline, which it wouldn't have done when I learnt to drive.

So true is the saying: "you pass your test THEN you learn to drive!!"

[Jan van de Wouw]

Ah, you took your lessons in a CVT? That's even more different, as a CVT (Dutch invention!)

has no separate geras at all, so a CVT should shift without any jolting at all, where

a conventional automatic DOES jolt the car a little bit and so does the "robot-box".

If you really have "trouble" with your car you could ask your instructor

if he of she could give you some pointers with your specific car...

[miss_d_bus]

Ah, you took your lessons in a CVT? That's even more different, as a CVT (Dutch invention!) has no separate geras at all, so a CVT should shift without any jolting at all, where a conventional automatic DOES jolt the car a little bit and so does the "robot-box".

If you really have "trouble" with your car you could ask your instructor if he of she could give you some pointers with your specific car...

It is a bit of a difference! I learnt to drive in 2001-2002 so doubt I could track down my old instructor now, partly as I have moved house since then. I'm usually alright with the car. I feel I need a bit more patience with it at roundabouts and get a bit niggled with its speed of acceleration but I suppose thats a problem with all 1 litre engines!

I'm not sure why I am only now noticing these things and driven my Aygo for two years and not noticed?!? It might just be coincidence!!

I'm sure its just I am now paying more attention to the car and how it feels ;)

[boukehj]

If it's something that you've just noticed, after driving an MMT for 2 years, I would also consider the option that a trip to the dealer might be in order. I own an MMT Corolla Verso and it really takes a bit of getting used to (I've driven stick, a 'normal' automatic and a CVT as well). But again, given that you've been driving it for 2 years and now notice something new that sounds somewhat worrying (a car speeding up by itself), I would ask the dealer to have a look at it.

[miss_d_bus]

If it's something that you've just noticed, after driving an MMT for 2 years, I would also consider the option that a trip to the dealer might be in order. I own an MMT Corolla Verso and it really takes a bit of getting used to (I've driven stick, a 'normal' automatic and a CVT as well). But again, given that you've been driving it for 2 years and now notice something new that sounds somewhat worrying (a car speeding up by itself), I would ask the dealer to have a look at it.

Yes that is where my thoughts lay though I do take on board what Jan says about how the MMT functions but its down to the severity of it feeling like its speeding up by itself, though it isn't happening all the time. I hadn't driven from 2002 to 2007 so I think I had not got a lot to go on about how the MMT should feel. I better ring Toyota tomorrow and see what they say. I also seem to be able to turn my key in the ignition one notch further than its meant to go (and the car starts but no electrics) and by itself it then pings back and then the radio comes on so will probably get that looked at too whilst I'm in the area. As usual will have to wait an absolute age to get an automatic courtesy car as I can't see this being a quick job to sort if it is a problem and not a "feature of MMT".

Thanks for the help.

[another_pleb]

I was having a think about your problem.

Are you certain that the acceleration you describe is not just the car's transition between engine braking and the engine pulling the car as it does when you lift the clutch in 1st gear of a manual car without touching the accelerator?

I hope it's not the same "unintended acceleration" of the 1980s American market Audi 5000. (Stupid Yanks stamping on the throttle, thinking it was the brake. :o ) You bought an Aygo and have driven it successfully for 2 years so I'm doubly positive that you have a bit of sense ;)

[TonyAYGO]

Mine does it too, I notice it when im coming out of the multi storey car park every day. It only happens at low speeds, I always thought it was normal just to stop the engine from stalling

[AygoYugo]

I have a 07 reg automatic Aygo + 3dr.

Recently I have been having this strange feeling that my car accelerates a little by itself at low speeds.

Cath, if this continues after you have run out of petrol, will you marry me ??? :P

XXX

[uli]

Mine does it too, I notice it when im coming out of the multi storey car park every day. It only happens at low speeds, I always thought it was normal just to stop the engine from stalling

What TonyAYGO says is correct. I`ve anticipated this behaviour of my Aygo recently, too. The engine revs up to prevent stalling.

Regards, Uli

[miss_d_bus]

AygoYugo - I'm afraid my other half might have something to say about that haha. Definitely does it WITH fuel!!

I've got the car booked in to the garage to get the barrel lock on the ignition changed as its sticking (supposedly a known fault on a few Aygos!). It doesn't ping back after the engine is started like it is meant to. I've said to them about my feelings of the problems with the gearbox and they will test drive the car, probably use it to get the lunches in ;) I'll let someone who knows what the car is meant to feel like drive it about a bit and see if it is "just the car" and my imagination or something serious. They should quickly know if its not right HOPEFULLY!!!!

[miss_d_bus]

An update:

The car went into the garage and they reckoned it was the mat!

It might have been a factor but it did it again without the mat so I know it isn't that. It now does it in any gear and is incredibly scary as it went up 10 mph by itself up a hill.

Anyway, today I slow down for the traffic lights and go into first gear. The car then 'goes mad' and keeps revving like a boy racer by itself. I turn the engine off and start again and this time it does it in neutral. After a bit of panic and phone calling with the engine off, it is okay again for enough minutes to get the car off a dual carridgeway but I don't risk it and its stuck on a flat bed trailer and taken to Toyota to be fixed. The damn annoying thing is, is that the fault only so far appears when I am by myself so I am left with people probably thinking its all in my head!

[boukehj]

Awful that this happens. I don't think you should worry that at Toyota anyone would think it's in your head. What happened doesn't at all sound outrageous. It may be difficult to diagnose, though, because they might not be able to replicate it (although it seems to be getting worse, which is a good thing in that respect).

Don't worry too much, they'll find what part has worn out to the point that the computer thinks that what you needed was more throttle!

[benchan]

I think I got a similar problem with mine too, though not as bad.

I recently (end of last month) had the ecu reset because the car was shuddering a lot when in 1st gear - about two weeks later, I noticed my gas pedal was "sticky".

In my case it happens every now and then - once a week - when I am doing 30-40mph and when the car is shifting from 3rd to 4th...

[miss_d_bus]

Well, got the car back and they couldn't find the fault.

At the moment it is pointing towards interference caused by my amateur radio equipment in the computer system of the MMT gearbox. I've got to do a few tests to first rule this out by changing transmitter powers and antenna location and try for a week or so with the kit swtiched off.

If this is the cause, it is bad that they manufacture a car that is not sufficiently shielded from electromagnetic sources and causes very dangerous problems.

I've already had issues with my central locking being jammed by radio repeater equipment operating on 433 MHz running at my house but it was sorted after a frequency change on the home equipment. Its a real annoyance that the UK government put car central locking systems on the same frequencies as radio amateurs (with the highest licence) who can transmit legally up to 400w. I suspect the problem is very widespread and caused by Ofcom's daft management of the radio spectrum.

I hope the fix with the gearbox is as simple as changing some settings on my radio. *Fingers crossed*

Anyone heard of this problem before?

[Wild west Drifter]

Hope its nothing major, Trouble is we don't have exclusive use of 430 Mhz.

Have you got your radio or the cables on the drivers side because the mmt has an electronic throttle?

Have you tried using a near field detector to see if any harmonics are being emitted from the cable that could cause problems also crimped co-axial cables are more prone to causing problems than soldered ones. Needs to be BNC or N type for 70cms PL259's are very lossy above 250Mhz.

As a side note also can get problems using HF mobile not least because of the antenna sizes, used to run 14Mhz mobile and that was a bumper mount on a 4x4. Have run most bands mobile but 23cms was the worst- a wet leaf caught against the whip would totally screw up the SWR.

[miss_d_bus]

Hope its nothing major, Trouble is we don't have exclusive use of 430 Mhz.

Have you got your radio or the cables on the drivers side because the mmt has an electronic throttle?

Have you tried using a near field detector to see if any harmonics are being emitted from the cable that could cause problems also crimped co-axial cables are more prone to causing problems than soldered ones. Needs to be BNC or N type for 70cms PL259's are very lossy above 250Mhz.

As a side note also can get problems using HF mobile not least because of the antenna sizes, used to run 14Mhz mobile and that was a bumper mount on a 4x4. Have run most bands mobile but 23cms was the worst- a wet leaf caught against the whip would totally screw up the SWR.

All the cables are on the left side with the radio under the passenger seat and the head unit extended to the front of the car.

I've not checked for harmonics but will ask around and see if any locals might have some kit that can help me test this.

The antenna itself is a glass mount 1/2 wave on the windscreen on the top left with supplied coax of a specific length that cannot be cut as its tuned. I'd guess the plug is a crimped N type but not sure off the top of my head.

Before I had a 1/4 wave mini mag mount on the back of the car.

I probably should look into whether too much current being drawn is another issue because I know that on 50w on 2m, the headlights dim. I wonder if thats got anything to do with it.

I'm testing at the moment to see if the problems go away with the APRS on 2m off and no chatting on the radio so currently QRT :(

[Cyker]

Argh... it seems it isn't just you miss_d!

http://abcnews.go.com/print?id=8980479 ( Saw it on http://tech.slashdot.org/story/09/11/04/00...ners-Up-In-Arms )

This seems to be mainly for larger Toyotas in the USA, but there might be a link.

[miss_d_bus]

This seems to be mainly for larger Toyotas in the USA, but there might be a link.

Hmmm I would assume that fault would be specific to the full automatics, and not the MMTs however, it is scary when it feels like the car has a mind of its own. In my case, the car will slow down with the brake.

Today at a roundabout, the car was in 1 gear and started revving by itself but seemed to sort itself out. It did it last Tuesday too and I couldnt get it to stop again without turning the engine off. Oddly its the same road...! I looked about for any antenna masts etc but its a road that cuts between a council estate so I suspect the only transmitters about would be for CB!

Oh and my radio kit is unplugged and no mats in use.

I did notice there is a similar pattern to an issue I saw with Yarises on here:

http://toyotaownersclub.com/forums/index.php?showtopic=87111

There is no beeping except rarely in reverse or any feeling or indication that the car is going into neutral by itself. The revving only happens when the car is stationary, i.e. in traffic queues.

I've relayed the symptoms to a Pug/Citreon mechanic and he suggested issues with ECU. Could it be that and/or the clutch actuator?

Since I've only driven a manual about 5 times, I don't know what it means when a clutch slips or how it should feel.

I'm so cross with it that I'm thinking of trying to learn how to drive a manual car even though its going to be a physical challenge for when I get the next car.

[aygoal]

Are these rev rising 'features' become more prevalent now the weather is getting colder and the auto chokes are raising the revs more? When the engine is cold I find the revs slower to drop when you dip the clutch in our 1.33 Yaris

Re the key, I found on our Aygo that my key (the blank key) was sometimes a bit stiff, whereas the wife's key (the remote one) would be as smooth as hot knife through butter....

[miss_d_bus]

Are these rev rising 'features' become more prevalent now the weather is getting colder and the auto chokes are raising the revs more? When the engine is cold I find the revs slower to drop when you dip the clutch in our 1.33 Yaris

Re the key, I found on our Aygo that my key (the blank key) was sometimes a bit stiff, whereas the wife's key (the remote one) would be as smooth as hot knife through butter....

I don't think it is weather related as its been going on for a while but half the problem is that I don't now know if its in my head, how the car is meant to be or a fault! Its got all confused in my head and my memory is failing me so I am thinking of asking if I can test drive another Aygo MMT to compare, to put my mind at rest lol!

The key sticking problem is a known issue with the Aygo and I understand its seen a bit at garages so worth getting done under the warranty as its not a big job. I've not tried my blank spare key so I'm not sure if that would be fine. The issue I had was it sticking so I guess that would happen with the other key if I tried it.

[aygoal]

Are these rev rising 'features' become more prevalent now the weather is getting colder and the auto chokes are raising the revs more? When the engine is cold I find the revs slower to drop when you dip the clutch in our 1.33 Yaris

Re the key, I found on our Aygo that my key (the blank key) was sometimes a bit stiff, whereas the wife's key (the remote one) would be as smooth as hot knife through butter....

I don't think it is weather related as its been going on for a while but half the problem is that I don't now know if its in my head, how the car is meant to be or a fault! Its got all confused in my head and my memory is failing me so I am thinking of asking if I can test drive another Aygo MMT to compare, to put my mind at rest lol!

The key sticking problem is a known issue with the Aygo and I understand its seen a bit at garages so worth getting done under the warranty as its not a big job. I've not tried my blank spare key so I'm not sure if that would be fine. The issue I had was it sticking so I guess that would happen with the other key if I tried it.

No worries, I hope you get it sorted - which dealer is your local?

Our Aygo is now at the dealers waiting for a new loving owner. As our driving is now 90% motorway we thought a new Yaris 1.33 would be more suitable.

[grahamsmythe]

We have EXACTLY the same problem with our 06 Plate Semi-Automatic Aygo.

Anyone got an idea what the problem is?

[miss_d_bus]

We have EXACTLY the same problem with our 06 Plate Semi-Automatic Aygo.

Anyone got an idea what the problem is?

Hmmm thats very interesting Graham. I am taking my car into Toyota Canterbury next week and will be driving another Aygo MMT for two days so I will get a good opportunity to compare.

I have ruled out the mats and the amateur radio kit so right now its still a mystery with no warning light appearing. There is no record of any other garage with this fault with Toyota UK either.

Out of interest, do you feel like the accelerator pedal sticks intermitently? I am starting to think its that because I can put my foot underneath the pedal and lift it up and the problem goes away! The spring on the pedal has been checked and its functioning fine so right now its pointing towards a sensor problem but who knows?! It can be a very scary experience, particularly with a car that feels a bit out of control. I live at a top of a very steep hill on a cliff with a sharp bend half way down thats a known spot for fatalities. I'm keen not to become part of the local RTA stats... Lets say if brakes failed, I'd be part of those stats...

Yet I feel the problem isn't taken as seriously as it should be - when the car is not functioning correctly, its flippin' dangerous and frightening!!!

What I do know is that I was going up a hill on the A2 between Dover and Canterbury in 5th gear where there was roadworks and I was having serious trouble keeping within the 50 mph speed limit. I had to keep braking to keep myself within 50 mph. As soon as I took my foot off the brake, the car wanted to tear off without my foot on the accelerator! The worst bit was there was a police motorcycle behind me :( He must of thought I was a right nutter with the brakelight keep coming on.

I wonder if anyone else has experienced anything like this ?!