Does anyone know anything about a flat spot that has suddenly appeared on my 2.2D estate of 07 vintage. It occurs between 1000 and 1800 RPM. It doesn't manifest until the engine is warm. It occurs when on a trailing throttle and I try to gently accelerate, it the seems to hesitate and then causes a bit of transmission shunt. This started all of a sudden one morning. Prior to that the glow plug warning light came on occasionally but could be extinguished with a quick re-start.