I should clarify...the "lurch" is different from the problem I have discussed. The issue I have had is a surge...same as described at the start of this thread. Happens when cruising at a steady rate and lower rpms...car tends to rock. It could be mistaken for a hestitation in the ignition or fuel systems as the revs move up and down slightly...you can actually hear the change as well as feel it. Apparently, the torque converter is moving in and out of lock up and as a result the car surges. My vehicle is a 2004 XKR...it can happen in any ZF six speed equiped car. Torque converter replacement has cured the problem.