Torque Converter Lock-Up
WARNING: This page is about a different car, the 1995 Mercury Villager. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of the automatic transaxle torque converter lock-up feature is to eliminate power loss of torque converter stage when vehicle is in cruise condition. Converter clutch will engage under the following conditions: vehicle is moving faster than a precalibrated speed, engine is at normal operating temperature, throttle position sensor output is not changing (indicating a steady road speed), transaxle is in high gear, and brake switch is closed.