Cellular automata path and fill algorithm

I have worked for a few days in my cellular automata path algorithm and an easy fill algorithm, but sometimes I get some weird fall in my FPS.

If you need a preview

function createGrid()
{
// Create Grid
for(var y = 0; y < yTotal; y++)
{
  grid[y] = [];
    for(var x = 0; x < xTotal; x++)
  {
       grid[y][x] = RandomRange(0, 1);
  }
}

// 6 loops, why? just to make the path more straight
for(var i = 0; i < 6; i++)
{
  for(var y = 0; y < yTotal; y++)
  {
    for(var x = 0; x < xTotal; x++)
    {
      var total = 0;
      // All neighbour values added to the current one
      for(var h = -1; h <= 1; h++)
      {
        for(var w = -1; w <= 1; w++)
        {
          var yw = Math.max(0, Math.min(xTotal - 1, y + h)),
              xw = Math.max(0, Math.min(yTotal - 1, x + w));
              total += grid[yw][xw];
        }
      }
      // Make current to wall or air
      grid[y][x] = Math.round(total / 3) & 1;
    }
  }
}

// If current Cell has value of 0, it will be air elsed wall
for(var y = 0; y < yTotal; y++)
{
  for(var x = 0; x < xTotal; x++)
  {
       grid[y][x] = grid[y][x] == 0 ? new Air("white") : new Wall("black");
  }
}
}

Draw and fill algorithm:

setInterval(function(){

ctx.clearRect(0, 0, wCanvas, hCanvas);

for(var y = 0; y < yTotal; y++)
{
  for(var x = 0; x < xTotal; x++)
  {
    var celd  = grid[y][x];

    // Fill Algorithm
    if(celd instanceof Fill)
    {
      // Just to make a delay
      if(celd.TotalCooldown-- === 0)
      {
        var xLeft   = Math.max(0  , x - 1),
            xRight  = Math.min(xTotal - 1 , x + 1),
            yTop    = Math.max(0  , y - 1),
            yBottom = Math.min(yTotal - 1 , y + 1);

        if(grid[y][xRight]  instanceof Air) grid[y][xRight]   = new Fill("red");
        if(grid[y][xLeft]   instanceof Air) grid[y][xLeft]    = new Fill("red");
        if(grid[yBottom][x] instanceof Air) grid[yBottom][x]  = new Fill("red");
        if(grid[yTop][x]    instanceof Air) grid[yTop][x]     = new Fill("red");
      }
    }

    // Draw Map
    ctx.beginPath();
    ctx.fillStyle = celd.Color;
    ctx.rect(x * celdSize, y * celdSize, celdSize, celdSize);
    ctx.fill();
    ctx.closePath();
  }
}
}, 1000 / 60);