Why this simple code doesnt work?

Hello guys, I'm a bit of beginner to Unity and after hours and hours of trying I decided to ask some help here. I have this piece of code (which is simple vehicle physics) which works very well on Windows:

void FixedUpdate () {

//Input

float inputGas = Input.GetAxisRaw("Horizontal"); //

     JointMotor motor = LeftWheel.hingeJoint.motor;
     motor.force = (inputGas!=0?1:0) * 30;
     motor.freeSpin = true;
     motor.targetVelocity = -inputGas * 4000;

     LeftWheel.hingeJoint.useMotor = inputGas != 0;
     LeftWheel.hingeJoint.motor = motor;

     RightWheel.hingeJoint.useMotor = inputGas != 0;
     RightWheel.hingeJoint.motor = motor;

     rigidbody.AddRelativeTorque(0, 0, -inputGas * 3000);

} Good, it works because h is either -1 or 0 or +1 and it's constant while pressing the button.

But then I want to make it for touchscreens and the physics starts doing some very weird stuff (like switching between h=1 and h=0 very very fast or something) , and h is +1 apparently:

void FixedUpdate () {

//Input foreach (Touch touch in Input.touches) { if (gas.HitTest(touch.position) && touch.phase == TouchPhase.Stationary) { inputGas = 1; } else if (gas.HitTest(touch.position) && touch.phase == TouchPhase.Ended) { inputGas = 0; } }

// JointMotor motor = LeftWheel.hingeJoint.motor; motor.force = (inputGas!=0?1:0) 30; motor.freeSpin = true; motor.targetVelocity = -inputGas 4000;

     LeftWheel.hingeJoint.useMotor = inputGas != 0;
     LeftWheel.hingeJoint.motor = motor;
     
     RightWheel.hingeJoint.useMotor = inputGas != 0;
     RightWheel.hingeJoint.motor = motor;
     
     rigidbody.AddRelativeTorque(0, 0, -inputGas * 3000);

}

What I am doing wrong? I have tried putting the input in a Update() function to be independent of the framerate, but some weird stuff is still happening.

Thanks a lot guys!