I have a 2000 celica. Rpms drop and car stalls when shiftig from second to 3rd.

if your ck eng light is on scan codes and post so we can adv.you may also want to clean throttle body to see if that helps,could be all coked up inside

could be bad torque converter lock up solenoid but I would do what greg said and have it checked for codes

check proper atf level