By mechanically linking the turbine to the pump, it results in a ‘lock-up’ affliction, primarily reworking the fluid coupling into a rigid coupling, akin to your locked handbook transmission clutch. If the torque converter is faulty, it would build sudden pressures inside the torque converter, which can induce tough idling. https://edwinnsssr.kylieblog.com/34805412/a-secret-weapon-for-torque-converter-clutch