Particle dont dissapear and leave trail behind ship :(

Unity Engine
1

I have big problem with my particles :confused:

Imgur

When I move my ship with “wsad”, particle leave trail behind the ship - they should disapear I think but they dont :/. Could anyone can help me with this? Without destroying particles, everything sucks…

Here is my whole script :
I got thir error and meyby this is the problem:
Assets/Moje_Skrypty/LookAtMouse.cs(73,28): warning CS0219: The variable `showEngine’ is assigned but its value is never used

using UnityEngine;
using System.Collections;
 
public class LookAtMouse : MonoBehaviour
	
{
 
	// speed is the rate at which the object will rotate
	public float speed;
	public float shipSpeed;
	public GameObject engine;
	public GameObject enginePrefab;
	public bool engineStarted;
	public GameObject  showEngine;
	
	
 
	void FixedUpdate () 
	{
    	
    	Plane playerPlane = new Plane(Vector3.up, transform.position);
 
    	
    	Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);
 
    	
    	float hitdist = 0.0f;
    	
    	if (playerPlane.Raycast (ray, out hitdist)) 
		{
        	
        	Vector3 targetPoint = ray.GetPoint(hitdist);
 		
		
		
		
        	
        	Quaternion targetRotation = Quaternion.LookRotation(targetPoint - transform.position);
 
        	
        	transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, speed * Time.time);
			
			
			if (Input.GetKey("w") || Input.GetKey("s") || Input.GetKey("a") || Input.GetKey("d"))
			//if(silnikiodpalone == false)
			{
				startEngine();	
			}
			else
				
			{
				stopEngine();
				
			}
		float movingShipAxisX = Input.GetAxis("Horizontal") * shipSpeed * Time.fixedDeltaTime;
		transform.Translate(Vector3.right * movingShipAxisX, Space.World);
		
		
		float movingShipAxisY = Input.GetAxis("Vertical") * shipSpeed * Time.fixedDeltaTime;
		transform.Translate(Vector3.forward * movingShipAxisY, Space.World);
		}
		
		
		
		
		
    }
	
	void startEngine()
	{
		//if(engineStarted == false)
		{
		GameObject showEngine = (GameObject)Instantiate(enginePrefab, engine.transform.position, engine.transform.rotation);
		}
		//engineStarted = true;
	}
	
	void stopEngine()
	{
		Destroy(showEngine);
		
	}
	
	
}
2

Try

showEngine = (GameObject)Instantiate(enginePrefab, engine.transform.position, engine.transform.rotation);