5 ms·

In such cases, if you can't brake or release the throttle, one other out is to gear-shift into neutral. The result of slamming that power into neutral won't be

In such cases, if you can't brake or release the throttle, one other out is to gear-shift into neutral. The result of slamming that power into neutral won't be great for the engine or transmission, but at least you'll be able to stop accelerating and coast to a stop.

macintux 4y ago
I recall riding with a friend who had an automatic, and his engine was racing at every stoplight (I don't recall the name of the hardware that's supposed to disengage the engine when the brake is fully applied, but clearly it was broken). So, he sat at every light with the brake pushed hard to the floor, trying to keep it from plunging into the intersection. As a long-time stick shift driver, I asked him why he didn't just shift it into neutral.
- hatsunearu 4y ago
  uh what the fuck? why didn't he fix the damn car?
  - sokoloff 4y ago
    I suspect a lot of people find themself in a situation where driving a car with a mechanical problem is a sensible local optimum for some period of time. The statute of limitations has passed on all of my “she’ll be a’ight” endeavors, but they included having to manually apply throttle to keep the engine lit, driving on partial service brakes, driving without a working charging system, having to push start the car, reckoning speed by gear and RPM, and fueling based on ded reckoning with an INOP fuel gauge and odometer.
    - throwaway0a5e 4y ago
      The partial brakes is the only thing on that list I'd consider to be more than just an inconvenience. Obviously if you want to drive like a jerk you need the car to be in tip top shape so that you have the most freedom to make control inputs but if you just want to putt along and drive in a mild mannered way having a bunch of mechanical oddities that constrain what you can do isn't a big deal.
    - dotancohen 4y ago
      I notice that a lot of people who have never driven 1980's era and earlier cars have no idea that cars were _always_ broken in some form or another. Every single car had developed some problem or another every year, one simply got used to this car having a bad window motor, that car having a bad started solenoid, this one torque steering to the left, that one thumping on brakes, this other one running rough when driving to the east, that one leaks transmission fluid, that other one won't restart after five minutes but will restart after half an hour, this one has no A/C, this one has terrible wind noise, this one blinks left when the radio is on FM, this one drips radiator fluid into the cabin when the heat is on, that one will spontaneously activate ABS in the last second before coming to a complete stop 50% of the time, this one squirts washer fluid onto the roof of the car to your right, this one dims the dash lights when the radio DJ talks instead of playing music, that one overheats, etc etc.
- winrid 4y ago
  There is no hardware to disengage the engine when your brake is pressed. The torque converter just allows some slip so you can stop. Likely he just had a high idle due go some vacuum leak or whatever, as you said.
- 2143 4y ago
  > I asked him why he didn't just shift it into neutral. What if the engine free-revs and redlines on neutral? Maybe turning it off might be a safer alternative.
  - dotancohen 4y ago
    > Maybe turning it off might be a safer alternative. Young drivers might not understand the difference between the powered-down and the pull-the-key-out positions. There is a real danger of locking the steering wheel in this case.
    - ranger_danger 4y ago
      Most cars today do not have traditional keys in an ignition cylinder.
  - sidewndr46 4y ago
    Even very old cars have a rev limiter based off the RPM that momentarily disables the ignition.
    - gonzo 4y ago
      Define “very old” because this is not true without an ECU
      - sidewndr46 4y ago
        You don't need an ECU to act as a rev limiter. Gasoline engines have had rev limiters in all different kinds and types for over 100 years. Some cut fuel, some cut spark, some cut both. For example pre 1900: https://en.wikipedia.org/wiki/Hit-and-miss_engine https://en.wikipedia.org/wiki/Hit-and-miss_engine Later: https://www.jalopyjournal.com/forum/threads/mechanical-rev-limiters-whos-used-one.1001470/ https://www.jalopyjournal.com/forum/threads/mechanical-rev-l... 1970s electronic type: https://www.428cobrajet.org/id-governor https://www.428cobrajet.org/id-governor Even my push mower has a rev limiter, it just gets called a governor on that engine. The majority of large American engines used the valves as the rev limiter. The valve springs were so weak that past a certain RPM the performance of the engine falls off so fast it isn't going to rev anymore, even in neutral. The valves never fully close, so performance is very poor. This is well below the mechanical limitations of the crankshaft, so nothing is really going to happen. Once interference engines showed up as common place in the market, it became mandatory to have a rev limiter. This happened as electronic ignition and fuel injection became more common, so it was logically incorporated into the ECU as time went on.
twofornone 4y ago
Shifting to neutral under load is probably not harmful. It's the opposite that is harsh on the drivetrain. However if the throttle is stuck and you are in neutral you'll end up revving at redline until you turn off the engine. Not the end of the world momentarily but you don't want to leave the engine revving that high for a prolonged period of time.

macintux 4y ago

I recall riding with a friend who had an automatic, and his engine was racing at every stoplight (I don't recall the name of the hardware that's supposed to disengage the engine when the brake is fully applied, but clearly it was broken). So, he sat at every light with the brake pushed hard to the floor, trying to keep it from plunging into the intersection. As a long-time stick shift driver, I asked him why he didn't just shift it into neutral.

hatsunearu 4y ago
uh what the fuck? why didn't he fix the damn car?
- sokoloff 4y ago
  I suspect a lot of people find themself in a situation where driving a car with a mechanical problem is a sensible local optimum for some period of time. The statute of limitations has passed on all of my “she’ll be a’ight” endeavors, but they included having to manually apply throttle to keep the engine lit, driving on partial service brakes, driving without a working charging system, having to push start the car, reckoning speed by gear and RPM, and fueling based on ded reckoning with an INOP fuel gauge and odometer.
  - throwaway0a5e 4y ago
    The partial brakes is the only thing on that list I'd consider to be more than just an inconvenience. Obviously if you want to drive like a jerk you need the car to be in tip top shape so that you have the most freedom to make control inputs but if you just want to putt along and drive in a mild mannered way having a bunch of mechanical oddities that constrain what you can do isn't a big deal.
  - dotancohen 4y ago
    I notice that a lot of people who have never driven 1980's era and earlier cars have no idea that cars were _always_ broken in some form or another. Every single car had developed some problem or another every year, one simply got used to this car having a bad window motor, that car having a bad started solenoid, this one torque steering to the left, that one thumping on brakes, this other one running rough when driving to the east, that one leaks transmission fluid, that other one won't restart after five minutes but will restart after half an hour, this one has no A/C, this one has terrible wind noise, this one blinks left when the radio is on FM, this one drips radiator fluid into the cabin when the heat is on, that one will spontaneously activate ABS in the last second before coming to a complete stop 50% of the time, this one squirts washer fluid onto the roof of the car to your right, this one dims the dash lights when the radio DJ talks instead of playing music, that one overheats, etc etc.
winrid 4y ago
There is no hardware to disengage the engine when your brake is pressed. The torque converter just allows some slip so you can stop. Likely he just had a high idle due go some vacuum leak or whatever, as you said.
2143 4y ago
> I asked him why he didn't just shift it into neutral. What if the engine free-revs and redlines on neutral? Maybe turning it off might be a safer alternative.
- dotancohen 4y ago
  > Maybe turning it off might be a safer alternative. Young drivers might not understand the difference between the powered-down and the pull-the-key-out positions. There is a real danger of locking the steering wheel in this case.
  - ranger_danger 4y ago
    Most cars today do not have traditional keys in an ignition cylinder.
- sidewndr46 4y ago
  Even very old cars have a rev limiter based off the RPM that momentarily disables the ignition.
  - gonzo 4y ago
    Define “very old” because this is not true without an ECU
    - sidewndr46 4y ago
      You don't need an ECU to act as a rev limiter. Gasoline engines have had rev limiters in all different kinds and types for over 100 years. Some cut fuel, some cut spark, some cut both. For example pre 1900: https://en.wikipedia.org/wiki/Hit-and-miss_engine https://en.wikipedia.org/wiki/Hit-and-miss_engine Later: https://www.jalopyjournal.com/forum/threads/mechanical-rev-limiters-whos-used-one.1001470/ https://www.jalopyjournal.com/forum/threads/mechanical-rev-l... 1970s electronic type: https://www.428cobrajet.org/id-governor https://www.428cobrajet.org/id-governor Even my push mower has a rev limiter, it just gets called a governor on that engine. The majority of large American engines used the valves as the rev limiter. The valve springs were so weak that past a certain RPM the performance of the engine falls off so fast it isn't going to rev anymore, even in neutral. The valves never fully close, so performance is very poor. This is well below the mechanical limitations of the crankshaft, so nothing is really going to happen. Once interference engines showed up as common place in the market, it became mandatory to have a rev limiter. This happened as electronic ignition and fuel injection became more common, so it was logically incorporated into the ECU as time went on.

twofornone 4y ago

Shifting to neutral under load is probably not harmful. It's the opposite that is harsh on the drivetrain. However if the throttle is stuck and you are in neutral you'll end up revving at redline until you turn off the engine. Not the end of the world momentarily but you don't want to leave the engine revving that high for a prolonged period of time.