Problem with jcar script for android mobile

Hello everybody :D I have again some problem's with some scripting :( So my problem is what i use is (ctrl-j) jcar script . But i can't make it so that i want to don't use the accelerometer for acclerating and for reverse . I want instead (accelerometer) to press a certain button (like gas,brake pedal etc..) But i want to have steering with accelerometer so steering don't need editing :)

 using UnityEngine;
 using System.Collections;
 
 public class JControlledCar : JCar {
     
     // automatic, if true car shifts automatically up/down
     public bool automatic = true;
 
     public float shiftDownRPM = 1500.0f; // rpm script will shift gear down
     public float shiftUpRPM = 2700.0f; // rpm script will shift gear up
 
     void Update() {
         if (Input.GetKeyDown("page up")) {
             ShiftUp();
         }
         if (Input.GetKeyDown("page down")) {
             ShiftDown();
         }
         if (Input.GetKeyDown("g")) {
             automatic = !automatic;
         }
         if (Input.GetKeyDown("t")) {
             switch (wheelDrive) {
                 case JWheelType.Front : wheelDrive = JWheelType.All; break;
                 case JWheelType.Back : wheelDrive = JWheelType.Front; break;
                 case JWheelType.All : wheelDrive = JWheelType.Back; break;
             }
             foreach (WheelData w in wheels) {
                 WheelCollider col = w.col;
                 col.motorTorque = 0f;
                 col.brakeTorque = 0f;
             }
         }
     }
 
     
     // handle the physics of the engine
     void FixedUpdate () {
         
         float steer = 0; // steering -1.0 .. 1.0
         float accel = 0; // accelerating -1.0 .. 1.0
         bool brake = false; // braking (true is brake)
         
 //        if ((checkForActive == null) || checkForActive.active) {
 //            // we only look at input when the object we monitor is
 //            // active (or we aren't monitoring an object).
 //            steer = Input.GetAxis("Horizontal");
 //            accel = Input.GetAxis("Vertical");
 //            brake = Input.GetButton("Jump");
 //        }
         if ((checkForActive == null) || checkForActive.active) {
             // we only look at input when the object we monitor is
             // active (or we aren't monitoring an object).
 
             // don't know if I guessed the right axi (what's plural for axis?) here
             // now you have to hold the iphone more or less flat and move from there
             // just experiment with it, for really good control you maybe have to look
             // for something more advanced like averaging the samples to get less
             // jitter and stuff.
             steer = -Input.acceleration.y;
             accel = Mathf.Clamp(4f * (-Input.acceleration.z -0.5f), -1f, 1f);
 // Debug.Log("v = " + iPhoneInput.acceleration + " accel = " + accel);
             // for brake I only check if there is a touch started or going on
             for (int i = 0; i < Input.touchCount; i++) {
                 Touch touch = Input.GetTouch(i);
                 if ((touch.phase != TouchPhase.Ended) && (touch.phase != TouchPhase.Ended)) {
                     brake = true;
                 }
             }
         }
         
         // handle automatic shifting
         if (automatic && (CurrentGear == 1) && (accel < 0.0f)) {
             ShiftDown(); // reverse
         }
         else if (automatic && (CurrentGear == 0) && (accel > 0.0f)) {
             ShiftUp(); // go from reverse to first gear
         }
         else if (automatic && (MotorRPM > shiftUpRPM) && (accel > 0.0f)) {
             ShiftUp(); // shift up
         }
         else if (automatic && (MotorRPM < shiftDownRPM) && (CurrentGear > 1)) {
             ShiftDown(); // shift down
         }
         if (automatic && (CurrentGear == 0)) {
             accel = - accel; // in automatic mode we need to hold arrow down for reverse
         }
         if (brake) {
             accel = -1f;
         }
         
         HandleMotor(steer, accel);
     }
 }

I hope that it's everything is clear .

I really hope that some one can help me :)