Accelerator stuck wide open while car is going fast: what should you do?

[NY]

This question was posed in a video reconstruction of an incident in the US.

You were offered three choices:

- yank on the handbrake

- put the car in neutral

- turn off the ignition

The "correct" answer was to put the car in neutral. Turning off the engine would lock the steering. Pulling on the handbrake would lock the rear wheels.

I'm not sure I agree with their answer.

I had this very thing happen to me - when I was learning to drive. I was going up a steep hill so I was in a low gear with the engine going quickly. When I got to the top and changed from second to third, the engine raced but I put it down to bad clutch/accelerator coordination. When it happened again as I changed to fourth, I realised it wasn't - especially as the car shot forward like a scalded cat.

I realised what had happened very quickly and also knew what would happen if I pressed the clutch or put the car into neutral, which was my first instinct: the engine would race very quickly and if it went well over the redline speed, it could well throw a piston which would be very bad news if all that fast-moving metal came to rest in an instant.

So somehow I managed very calmly to turn the ignition just far enough to kill the engine by putting it into the accessory position without turning all the way off. Had I been travelling "at 120 mph with the engine redlining" (as it said int he video) it might have been a *little* more difficult to turn it just the right amount. ;-)

Am I right that the last thing you want to do is let the engine greatly exceed its redline speed and risk it seizing up (I'm assuming that the car is old enough not to have a rev-limiter)? Do any steering locks actually lock the steering while the key is still in, even in the off position? I thought it only locked when the key was removed - for this very reason, so you can safely turn off the engine in the event of an emergency.

Discuss...

[Brian Reay]

No all cars have an Acc posn on the Ign switch.

You could use the handbrake partially, ie not full on.

Over reving the engine is the lesser of the evils compared to a high speed collision.

If you just turned off the engine on a manual, in neutral, then turn ign on, you could steer without power steering and have basic brakes.

[Jimbo in Bracknell ....]

could be worse....you could have had a chevy Nova when a engine mount broke the engine smashed the power brakes and pulled the accelerator cable giving full throttle......see the world in a chevy nova .....

[Chris Bartram]

Turning the engine off doesn't lock steering. That only happens when removing the key.

[DerbyBorn]

+1

[tabbypurr]

all the cars I had for decades* DO lock the steering with key in. I gather many don't now.

This is all very 101 stuff though. If someone can't work out what their options are, one can only hope they never have to deal with real life mechanical failure.

• at least the ones that had a steering lock

NT

[dennis]

Well on a manual car you can use the brakes to slow down and stall the engine on most cars.

[Michael Chare]

Depends on car. My current car has an electric steering lock which would come on if the ignition button was pressed. On most cars

[Michael Chare]

Depends on car. My current car has an electric steering lock which would come on if the ignition button was pressed. On most cars I would expect the foot brake to stop the car particularly a manual car in top gear.

[dennis]

While everyone else hasn't.

Rod is always the opposite of everyone else.

[TMS320]

Get the carpet off the pedal

Press the brake pedal. Hard and sustained. The engine is physically not capable of overriding. One hears about people claiming they tried to brake and it did nothing. Well, they must have just tried a few gentle jabs.

Turning off the ignition will turn off electric power steering. Not what you want to add to your list of surprises.

[Nick Finnigan]

It might be the correct first action with a US slushbox.

[GB]

I once went for a test drive in a Honda NSX supercar. Cruising along the motorway at a bit over 70, we came to some slower traffic, so I prudently decided to change from 6th gear into 4th. It's quite a narrow gate on the NSX, and I mostly drove automatic at the time, so I was quite out of practice.

The effect of going directly from 6th to 2nd at that speed is not catastrophic. It's a very finely engineered car. The engine is very responsive, and it makes an impressive noise when taken well over the red line in that way.

[GB]

The trouble is that you're probably catching up the traffic in front really fast. Looking down at the carpet doesn't occur to most people. They are too intent on gripping the steering wheel.

[Fredxx]

Probably the worst thing you could ever do.

[NY]

Why use the handbrake at all, if the footbrake is still working fine?

I was thinking in terms of a con rod breaking which would probably seize the crankshaft which would be bad news with the energy of the large mass of the flywheel having to be dissipated very rapidly as it came to rest, possibly locking the transmission (even with the slight clearance of a clutch pedal being pressed) and hence the wheels.

I don't know how fast an engine might turn if all the mechanical load is removed at full throttle, and how much extra load this would place on the con rods. Modern cars with fuel injection and and ECU would almost certainly have a rev limiter. But the car I was driving was much older than that, with a carburettor, so there would be no limit to the engine speed, other than normal engine friction and the maximum fuel flow that the carb could manage.

As it happens, the car no PAS and no servo brakes, so neither would have suffered.

I have since (in a much more recent car) driven with no PAS when my "fan belt" broke at 70 on the motorway. Getting the car off the motorway to a garage where I could wait safely for the RAC took a bit more effort to steer than normal, but was not impossible. Strangely the brakes did not seem to be affected, so maybe the brake servo is driven by something other than the "fan belt". Obviously on a car with an electric fan, the one thing that the belt does not drive is the radiator fan. Having seen the tortuous path that the belt ought to take (it had vanished and was probably in Lane 3 of the motorway) I wasn't going to attempt to jury-rig a replacement, even if I'd had anything to make a long enough loop. It's as easy as in the days of a longitudinal engine where the belt just goes round three pulleys (alternator, water pump and fan) and is at the front of the car, without loads of tensioning pulleys and very little space to work between the engine and the front wheel. Even the RAC man said it was virtually impossible on a modern car to replace the belt at the roadside, even if he carried the right spare for the car.

Would you believe after I had the belt replaced at my local garage, the replacement failed in the same way about 2000 miles later. The garage had failed to spot that the flanges of one of the pulleys were bent out of shape, which had shredded the replacement belt and may well have been the cause (rather than the side-effect) of the first belt failing. The garage denied all liability and wouldn't pay anything, so I stopped using them.

[Bob Eager]

Indeed. And keyless ignition is usually 'press the button and it all goes off'

Electric handbrake? (IYSWIM)

[Tosspot]

It's happened to me, 1850 Dolomite Sprint, just turn the engine off, it's not really a drama even at over a ton.

Sticky carb needle.

[Thomas Prufer]

I was a sometime passenger in a clapped-out VW bus where this happened fairly regularly.

The driver would press the clutch and remove his flip-flops (or, once, clogs), wrap his toes around the back of the accelerator, and pull it back up. Sorted.

An old VW engine doesn't get up to much speed in the moment that practiced driver took to do this. And the possibility of the car accelerating violently because of throttle stuck fully open was hoped for, but zero.

Thomas Prufer

[harry]

What if it's an automatic? The speed of most engines is limited by the "valve bounce" or the engine management system.. Theoretically, no damage should be caused.