Time.deltaTime problem

 using UnityEngine;
 using System.Collections;
 
 public class FPS_Controller : MonoBehaviour 
 {
     public GameObject playerBody, playerCamera;
 
     private float mouseX, mouseY, walkX, walkZ;
 
     [Range (1f,10f)]
     public float mouseSpeed, walkSpeed,;
 
     void Update () 
     {
         mouseX = mouseX + Input.GetAxis("Mouse X") * mouseSpeed * 10f;
         mouseY = mouseY + Input.GetAxis("Mouse Y") * mouseSpeed * 10f;
 
         if(mouseY > 90)
         {
             mouseY = 90;
         }
         if(mouseY < -80)
         {
             mouseY = -80;
         }
 
         playerCamera.transform.localEulerAngles = (Vector3.right * -mouseY);
         playerBody.transform.localEulerAngles = new Vector3 (0f, mouseX, 0f);
         
         if(Input.GetKey(KeyCode.W))
         {        
             playerBody.transform.position += playerBody.transform.forward * Time.deltaTime * walkSpeed;
         }
         if(Input.GetKey(KeyCode.S))
         {    
             playerBody.transform.position -= playerBody.transform.forward * Time.deltaTime * walkSpeed;
         }
         if(Input.GetKey(KeyCode.A))
         {    
             playerBody.transform.position -= playerBody.transform.right * Time.deltaTime * walkSpeed;
         }
         if(Input.GetKey(KeyCode.D))
         {    
             playerBody.transform.position += playerBody.transform.right * Time.deltaTime * walkSpeed;
         }
     }
 }

This code work very well but when i disable vSync the camera move very slowly. I also tryed with FixedUpdate, but doesnt work. The walk Part work with VSync enabled or disabled. Only the camera rotation doesnt work. Any solution?