Q: P1743 engine wants to stall when put in gear 2003 Ford Windstar

Hello - your car is stalling because the torque converter clutch is locked up and not releasing. It is acting just as a manual clutch would act if you kept your foot on the brake, and let the clutch out without giving the engine any gas. The engine stalls. The torque converter lockup clutch is inside of the torque converter, the fluid coupling that normally allows your engine to idle with the car in gear. The lockup clutch should only be engaged above 45 mph to improve cruising speed fuel efficiency. The P1743 problem code is an indicator of torque converter hydraulic circuit problems, possibly the solenoid which activates the lockup clutch. I recommend a stalls when put in gear inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, confirm this diagnosis, and give you an accurate assessment of damage and cost estimate for repairs.