Toyota accelerator recall

If you didn't know already, many Toyotas are being recalled because the accelerator may stick wide open. Originally it was claimed that the floormat got in the way. I don't believe that for a moment. Then an accelerator part that swelled up was replaced. Now the replacement is faulty.

Now Toyota say "The newly identified problem is caused by a mechanism that controls the accelerator pedal's return to the idle position after being pressed to the floor". Would that be a spring?

Since ordinary mechanics don't seem to have a clue about mechanical things like this, it's obviously a job for d-i-y people to look at. Not to fix, just to look at and see what the problem is.

I don't have a Toyota. Can people look at their Toyotas and tell us what the problem is? Perhaps post photos of the faulty part.

The official advice if the problem occurs is to shift into neutral. That would immediately wreck the engine of every car that I have ever owned, so clearly cars have changed a lot in recent years. It seems they don't even have an ignition switch that can be turned off, or if the engine can be turned off, many owners don't actually know how to do that. And these features are a great advance in reliability and safety, exactly why?

Reply to
Matty F
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In the US.

MBQ

Reply to
Man at B&Q

Turning the ignition off potentially locks the steering column lock and prevents you from steering. Not such a good plan if you're actually moving when your throttle sticks open.

Reply to
Dave Osborne

and Canada and Europe. If it's not a problem in the UK perhaps Toyota UK can tell Toyota Japan their secret solution to the problem.

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Motor Corp.'s (TM) Canadaian operations said Wednesday it is instructing dealers to suspend Canadian sales of its eight vehicles involved in a recall for sticking accelerator pedals, a day after it halted those vehicles' sales in the U.S. in an unprecedented move. ... Toyota will expand its recall of vehicles with defective gas pedals to Europe, a person close to the matter said Monday.

Reply to
Matty F

thought most modern cars have electronic rev limiters these days?

then switch it off and coast to a halt....what's the alternative?

JimK

Reply to
JimK

JimK gurgled happily, sounding much like they were saying:

And for the last twenty-odd years.

Reply to
Adrian

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I don't get the article here, just the headline - not sure if that's a Firefox issue, or a need to subscribe to WSJ before I can see the content (I did have a WSJ subscription, but no longer).

Which Toyotas does it affect? I doubt it's out late-90s US one somehow, but I can always look at the mechanism if it's relevant. From memory it's a couple of sliding plates and at least one spring at the "business end" (presumably because there are times when the ECU takes over despite what the manual cable-driven setup might be doing)

By "pressed to the floor" do they mean completely floored, or do they really mean "pressed toward the floor" (i.e. through the normal range of movement)?

cheers

Jules

Reply to
Jules

Some cars:

- The accelerator pedal operates a cable linkage to a butterfly valve inside the Throttle Body. The Throttle Body sits between the engine Intake Manifold (plastic/aluminium) and Airflow Meter (box after airfilter).

- When you floor the accelerator the cable pulls the throttle body butterfly valve fully open (butterfly means it folds in half backwards so as not to constrict airflow), this Wide Open Throttle (WOT) condition is detected by various means - usually a Throttle Position Sensor also mounted on the throttle body and the airflow meter which measures airflow mass (usually) or volume (dated) or pressure (very dated). Toyota even as late as early 1990 probably used Mass Airflow sensing (MAF).

- It is unlikely the Throttle Body spring is insufficient, they are usually brutally strong.

- It is more likely the accelerator pedal assembly is suffering stiction or an inadequate/deteriorating spring.

Other cars:

- Linkage between the accelerator pedal and engine is by electronic means only.

- The key benefit of this is engine responsiveness and better feedback control - throttle input signal itself is dampened avoiding hysterisis/ surge, with mechanical linkage the ECU tends to use other sensors to treat the effect of throttle hysterisis/surge which whilst reasonably effective with mass airflow suffer too much lag with volume airflow.

- Without a throttle body linkage (& spring) the accelerator pedal spring must act alone.

So either stiction or spring - or pedal assembly. I refer to pedal assembly because most accelerator pedals are non- linear in their action - a small initial pedal movement results in rapid RPM change to create a perception of a larger engine, whereas further larger RPM change requires larger pedal movement.

Another factor may be cruise control.

- With mechanical throttle linkage a cruise control system typically uses a vacuum canister, solenoid & ECU to pull on the pedal to maintain a particular RPM. The accelerator pedal can be seen to move up and down accordingly.

- With electronic throttle the control system may be the same (just operating on the throttle body) or electronic.

So fixing a spring at the pedal may not necesarily solve the problem. A few cars have been accused on "unattended acceleration" (USA side), that might as much be "unattended service schedules".

Such problems are more an issue for cars with automatic transmissions, they will just keep shifting under WOT. The solution like a manual transmission is to shift the into Neutral. The engine will redline however the RPM limiter will prevent immediate mechanical damage. The car coasts to a stop with power steering & brakes still operating normally. The engine is then turned off via the ignition switch.

Turning the ignition off whilst the vehicle is in motion should never be done - if in gear it will result in strong deceleration acting on the front wheels only, diminishing braking assistance, lost ABS, diminishing power steering and worst of all triggering the steering lock. If the vehicle is a runaway turbo diesel (dieselling on its own engine oil) it must be brought to a standstill and then with handbrake applied jammed into gear so as to stall the engine (or it will continue burning its own lubricating oil until failure). Quite an unrelated issue, just worth mentioning :-)

Reply to
js.b1

Umm, would the deceleration necessarily be any stonger than normal "lift off" deceleration. In most (?all) cars these days fuel is cut off on the overrun until rpm drops to idling speed.

Also, would brake assistance necessarily be lost? Plenty of vacuum for the servo as long as the car is in gear. I dare say there would be no ABS admittedly. Given the electronics involved in modern PAS I dare say you're right about that assisstance going.

Lastly, I've never had a car where *just* turning the ignition off has locked the steering. It's taken a further manoeuvre (like turning the key a bit further or removing the key) to engage the steering lock.

I'm not disagreeing with your general point of the inadvisability of turn off the ignition whilst in motion but I think some of your points are wrong.

Tim

Reply to
Tim Downie
7-

My Renault Scenic has a stop/start button. as soon as the button is pressed to stop, there's a click (presumably a relay ?) and the steering lock is *armed*. The slightest twitch of the wheel after that locks it.

Reply to
Jethro

On the face of it it sounds highly dangerous. What's to stop a bored child (or adult) pressing it whilst you're driving? Admitedly I don't know where the switch is sited but I'm sure some bored driver must have pressed it to see what happens.

My guess is that it won't activate the lock until the vehicle is stationary but that's just a guess.

Tim

Reply to
Tim Downie

You wouldn't notice on a Prius.

Reply to
Dave Plowman (News)

On *every* car I've ever owned with a steering lock - and that's plenty - you have to *remove* the key before the lock engages. Not just turn off.

Reply to
Dave Plowman (News)

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> Toyota Motor Corp.'s (TM) Canadaian operations said Wednesday it is

ManatB&Q is quite possibly correct in saying that UK cars are not involved. Toyotas are Japanese and as such designed and built as right hand drive cars, which means that they are ready for the UK, whereas those for USA, Canada and presumably the rest of Europe have to be modified to left hand drive. This begs the question whether the fault is in those modifications.

Reply to
Tinkerer

Why would that wreck the engine?

Reply to
The Medway Handyman

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Toyota Motor Corp.'s (TM) Canadaian operations said Wednesday it is

Of course UK cars have the pedal on the same side as Jap ones so may not be effected. But because there's a US recall, doesn't mean it will always apply elsewhere.

I had a front suspension leg collapse on my BMW. It's made of ally and the plate the spring bears on sheared off. Causing that side to sink - but more to the point cut through the wall of the tyre causing it to explode. Recall for this in the US and strengthening parts fitted. And the strut replaced if any cracks evident. BMW UK said it had never happened in the UK so not needed. A year later the other side did the same...

Reply to
Dave Plowman (News)

In message , "Dave Plowman (News)" writes

I remember a contractor saying he was late because his Sherpa van's engine had died in the older, single carriageway, wiggly Mersey tunnel. He had switched the ignition off to restart the engine and the steering had locked.

His actual excuse was that he had been buying a different vehicle.

It may just have been an excuse, of course.

Reply to
Bill

Well, I'd bet *your* life on it, but I wouldn't bet mine. ;-)

Reply to
Dave Osborne

Because on a vehicle without an electronic/mechanical governer to limit the maximum rpm to just below the red-line, holding the throttle open whilst the car is not in gear will just cause the engine rpm to rise rapidly to the maximum possible and in pretty short order, something would break.

Reply to
Dave Osborne

No it would not, but I emphasise it should it occur on a motorway. Losing engine power in the outside lane of a densely packed motorway can make negotiation to the inside lane very difficult. Remember you can no longer accelerate - yet must negotiate your way through lanes which may now be undertaking, including the HGV lane whose response time is far slower. I recall a driving simulator where people instinctly still hit the accelerator pedal as a conditioned response to loss of engine power despite it obviously not working.

Cars with a pressurised accumulator would be unchanged (aka "brake bomb"), cars with vacuum booster would be unchanged whilst the engine remains in gear but will suffer significant reduction after the first brake application when in neutral. Thus a driver shifting to neutral to extend deceleration time by freewheelling would quickly find they must press the brake pedal substantially harder after the first and successive application.

I suspect the majority of drivers would shift to neutral to extend the deceleration time to give themselves more time to negotiate a safe lane change across to the hard shoulder. In so doing they gain time, but add to the cognitive load of unfamiliar vehicle control - whilst negotiating a lane change through now undertaking traffic.

USA adds automatic gearboxes to the mix (kickdown increasing acceleration, reducing reaction time). The greatest risk is probably in a densely packed town near pedestrian areas.

A reality check is to visit the NHTSA. I have not checked the recall, but "unintended acceleration" due to design (stuck accelerator pedal or cruise control resume) has often been alleged but usually unprovable re vehicle crashed, inability to replicate failure mode in a lab and a million identical vehicles clocking up miles daily without incident. Human error and creative Defence Counsel more often than not. So I would not be surprised to find the recall says "may potentially" rather than "has been found to cause".

Mechanical throttle linkage designs had a failsafe whereby two springs, throttle body & accelerator pedal, could return the engine to idle. Electronic may only have one spring.

Never tried, I suspect that is true as long as the key remain in the ignition, although the key is not latched (retained). Despite not being latched I suspect withdrawal of the key would need to be complete for steering lock engagement to occur, rather unlikely someone is going to be fumbling to that extent.

Far from inadvisable, it is essential if the car is stuck WOT.

My comment re steering rack is invalid, keys remain in the ignition. My comment re loss of braking assist if shifted to neutral on some vehicles is not.

Thinking further, I have a suspicion most people would not switch the engine off. I think they would just declutch letting the engine hit the rev limiter and steer across the lanes - perhaps bringing the clutch up to accelerate again as necessary. It comes down to what environment the car is in - coming out of a junction in a crowded town centre with pedestrians around or cruising down a motorway. My suspicion is people will do the most *automatic* thing to remove the unintended acceleration, that is declutch, rather than turn the engine off. They may brake first, but quickly declutch probably as they feel (or smell) brakes fading.

They will react automatically by declutching, they will think whether to turn the engine off.

Reply to
js.b1

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