Why is not correctly working script?

Hello. please tell me why it does not work correctly the script

using UnityEngine;
using System.Collections;

public class CarController : MonoBehaviour {

 public WheelCollider[] WColForward;
 public WheelCollider[] WColBack;

 public float maxSteer = 30; //1
 public float maxAccel = 25; //2
 public float maxBrake = 50; //3


 // Use this for initialization
 void Start () {

}


 void FixedUpdate () {

 float accel = 0;
 float steer = 0;

 accel = Input.GetAxis("Vertical"); //4
 steer = Input.GetAxis("Horizontal"); //4 

 CarMove(accel,steer); //5

}

 private void CarMove(float accel,float steer){ //5

 foreach(WheelCollider col in WColForward){ //6
 col.steerAngle = steer*maxSteer; //6
}

 if(accel == 0){ //7
 foreach(WheelCollider col in WColBack){ //7
 col.brakeTorque = maxBrake; //7
 } 

 }else{ //8

 foreach(WheelCollider col in WColBack){ //8
 col.brakeTorque = 0; //8
 col.motorTorque = accel*maxAccel; //8
 } 
}
}
}

it kinda works but the impression that car like pulling his ears barely accelerates and barely turns. releasing the button stops abruptly. if you start to change the indicators that do not adequately behaves, that is, for example, starts to slow down when turning.
the lesson is taken from here: https://habr.com/ru/post/115557/