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For awhile now since getting my first car (and only driving Automatic transmissions) I've had plenty of experiences where when making a turn out of a parking lot with my wheels turned a bit too much, or even when I'm switching lanes on the highway (jumping 55 to 65 due to trucks ahead) it seems that if I floor my car or push the gas too much, I end up with a dangerous acceleration block where my engine revs and stays around 4k RPM, and the only way out has been to release the gas and floor again.

On the second round it usually accelerates normally, and typically this issue never comes up when I'm not immediately doing a full floor.

Anyway, I wanted to know what causes this issue and if it's specific to automatic transmissions or any car type, or if this is an issue across the board. In addition, any tips on prevention and getting out of the gear lock are greatly appreciated.

I know that misfiring can cause stalled acceleration, however every time my engine has misfired I promptly replaced the spark plugs and the check engine light always came on, and I have a code reader so I occasionally check even if the light isn't on.

Also I know that turning the wheels a bit too much might cause a bit more tension on acceleration, but shouldn't cars be able to make tight turns (such as when on a blind curve) rapidly?

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I have had cars that slip into neutral sometimes when turning a corner, and releasing the accelerator allowed it to go back in gear. I never did solve it, but I've seen it on more than one car. –  xpda Sep 15 '11 at 2:26
I can't remember well enough to make an answer but I think goes something like this: When you accelerate, the car tries to shift into higher gears. When you depress the peddle it pushes back to lower gears. This is why when you go up hills and start to slow, depressing the accelerator eventually pops you into a lower gear (with the jarring high rev to boot). This, however, could be way off base. –  Bob Roberts Sep 16 '11 at 20:27
Thank you both for the input. I had a feeling it had something to do with the transmission kicking up gears and such, but knowing that it does happen on other cars and not just mine is good to know. –  theonlylos Sep 18 '11 at 19:24
Here is an idea: do not floor it. I doubt you drive an Aston Martin, your car was not built for that. You can drive fast, but that does not mean scorching the rubber. Plan ahead, anticipate. Slow is smooth, smooth is fast (unless it is really slow). –  theUg May 31 '12 at 15:15

1 Answer 1

up vote 2 down vote accepted

What you are describing sounds like activation of the automatic's kickdown switch. Which is just that, a switch that forces the engine to downshift to provide more immediate acceleration. This is normal, and is usually a physical switch attached to the end of the gas pedal's travel path. It is activated when, say, 90% or more throttle depressed. Newer cars activate this just using the Throttle Position Sensor data.

Either way, this is designed in on automatic vehicles. Otherwise, if your car had just shifted into overdrive and you really need to accelerate, you'd have no way to force it to downshift (although some cars have a separate overdrive lockout switch). It is so your car can provide more immediate feedback. Think emergency situations, drag racing, late for work, etc.

When the kickdown switch is activated, the car will only downshift if possible. If you are already at 5000 RPM it will not downshift again and force the engine past its redline.

Usually upon letting off the pedal (not necessarily all the way) the car will shortly return to normal.

This is in addition to any programmed downshifting due to engine load. Which may be what you are encountering. A car is much harder to move with the wheels turned all the way, and depending on other factors, the car's computer may detect a large amount of engine load and downshift. Some cars handle this more gracefully than others.

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A pretty common problem for those that are used to driving a manual and get in an automatic. Can be very annoying/frustrating! I'll beg/borrow rides around when my car's in the shop just to avoid getting stuck with a rental that has an auto trans! –  Brian Knoblauch May 31 '12 at 14:56
Thanks very much for that through explanation - very insightful and good to know as I've had it happen on other cars but was wondering about the cause. –  theonlylos Jun 1 '12 at 4:32

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