Minecart and CMD block tp-ing don't work correctly

While in a minecart I attempted to use a command block to teleport me out of the cart to some coordinates. The minecart continued and I stop dead in the tracks, then when the minecart reached the end destination, aka a pit of lava to destroy it, I was teleported to the location of the lava pit. I checked the coordinates by activating the command block with the minecart on the rail by itself, they worked fine. The minecart was on a slope, heading down, on normal tracks and a single detector rail. Surrounded by black wool on both sides, not a space between the tracks and the block. The lava was covered by a piston until you hit the detector then the minecart falls in and the pistons pushes the block back out over the lava. Also I am not stuck in a minecart and do not have to click to get out.