My script to move a car works, but only once?..

Everything works in my script, the player presses W and the car moves, then I let go of W and it stops. But it only works once, I press W then let go, it works then after I press W for the second time after I let go, and nothing works....

wait(0.1)

local Plr = game.Players.LocalPlayer
local Mouse = Plr:GetMouse()
local Car = game.Workspace:FindFirstChild(""..Plr.Name.."'s_Car")
local Speed = 1000000

WIsDown = false

Mouse.KeyDown:connect(function(Key)
    if Key == "w" then
        if WIsDown == false then
            WIsDown = true
            local Force = Instance.new("BodyForce")
            Force.Parent = Car.Hitbox
            Force.force = Car.Hitbox.CFrame.lookVector * Speed
            Force.Name = "WForce"
        end
    end
end)

Mouse.KeyUp:connect(function(Key)
    if Key == "w" then
        if WIsDown == true then
            Car.Hitbox.WForce:Destroy()
        end
    end
end)

It's in a local script and output says: 10:38:16.793 - WForce is not a valid member of Part 10:38:16.794 - Script 'Players.Player.PlayerGui.WScript', Line 26