My 2001 Buick Regal will only start if press the gas pedal, when I release the gas pedal to step on the brake the engine shuts off. Any Ideas?

How To Reset the Service Engine Soon Light in a 1999 Buick...

1. Put the key into the ignition and turn it to "Run." Don't start the engine.
2. Press down slowly and fully on the gas pedal, then release it. Do this three times in five seconds.
3. Watch for the "Service Engine Soon" light to start blinking. This indicates that the system is resetting itself. ...
4. Start the Century's engine

1 First you will need to purchase a blank Toyota transponder key. You can do this from the dealership, a locksmith, or an online source such as eBay. Once you have the key, take the blank key and the master key to a locksmith that he or she can duplicate the key. This will be much cheaper than the dealership.

2 Now that you have the newly cut key and the master key, you can program the Toyota transponder key. Sit in the driver's side of the Toyota vehicle. Press and release the brake and gas pedal simultaneously.

3 Insert the master transponder key. Do not turn it. Push and release the gas pedal 5 times within at least 15 seconds of inserting the master key.

4 Press and release the brake pedal 6 times within 20 seconds of completing step 3, then remove the master transponder key.

5 Insert the newly cut transponder key into the ignition, but do not turn. Press the gas pedal once.

6 Wait up to 2 minutes or whenever the security light on the dashboard turns off. Once the light goes off, remove the new transponder key and press the brake pedal once. The new transponder key should now be programmed. Test the key by attempting to start the engine. If the engine does not start, repeat the steps above.

whts an idle control valve never hear of one whoever gave answer need t explain people aren't answering anything d u ptoff read these answers

Brake master cylinder faulty failing to release pressure.

it flooded. step on the gas pedal fully and crank the engine; that forces it to go into a clear flood mode by turning off the injectors. it may take a little while, but it will start.

To understand the problem with your car, you must first understand that when you are pressing down on the accelerator pedal with your foot, you are NOT "stepping on the GAS". You are actually stepping on the AIR. If you are having to open the accelerator in order to get the engine started, it is because the engine is not getting enough air to start on it's own. When you let up on the accelerator, you are shutting off the air.
It is the job of the Idle Air Control (IAC) solenoid (or motor) to allow enough air into the engine so the engine can idle when the accelerator is closed.

You MOST LIKELY have a bad IAC.

first -- make sure that you have brake fluid in the reservoir,, and on the back of the brake drums you will see where the brake lines enter the drum itself,, near there you will see a little ' zerk ' fitting -- to this fitting you should place a clear hose over this fitting and run it into a catch bottle,, now with the help of a buddy ( or wife ) -- have them sit in the car and get ready,, now you need to take a small wrench and turn ( counter clockwise ) the zerk fitting ( just a little ) --- while it is open have your helper step on the brake pedal AND HOLD DOWN to the floor,, at this point you need to close the zerk fitting --- have them release the pedal,, open the zerk again and have them press and hold the pedal again,, close the zerk and release the pedal,, do this 3 to 4 times until NO air bubbles can be seen through the clear hose --- also check and refill the reservoir to make sure you don't run it dry.
repeat this process on the other side. after both brakes have been done, check the brake pedal,, when you push down it should get hard ( stiffer ) ( pump a few times ) --- if it goes to the floor then you still have air in the system and need to repeat the bleeding process.

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Neutral Safety Switch may be out of rotational adjustment on the column.
And'/Or the Brake Switch is bad and is causing the Park lock to not release when pressing on the brake pedal.

Check out the TPS on the throttle body. It has three wires to it, The black is the ground and the other two are for high and low resistor readings. If an open occurs the car will die out and very well start again. The tps should have a 1.5 volt setting to operate correctly when new

It may be the throttle position sensor. You should have a check engine light on in your dash. You will need to have someone plug a OBD II reader in and retrieve the code.
You can spend a LOT of money just putting in one part after another.
Please let me know what you find.