Hello, my Sephia has a failure that appears intermittently, every now and then. When starting to drive at first gears, every time I accelerate, the car vibrates. As I release the accelerator, the vibration stops. And even more, the harder I accelerate, the stronger the vibration is. But as I set higher gears, the car vibrates less every time and, at 5th gear, it is not felt any more. I've already changed bearings, spark plugs wires and spark plugs, but the problem persists. Does anyone know anything about it?