Power Supply?

well i got the motors in today and they wont run using a 2cell battery when i take the jump the motors try to move but it never happens, if i remove this 2 cell holder and put the jumper back in and run everything using the 9v it works fine but... i have issues... if i use this code:

#include <AFMotor.h>

AF_DCMotor motor1(1);
AF_DCMotor motor2(2);

void setup() {

motor1.setSpeed(200); // set the speed to 200/255
motor2.setSpeed(200); // set the speed to 200/255
}

void loop() {

motor1.run(FORWARD); // turn it on going forward
motor2.run(BACKWARD); // turn it on going forward

}

Both motors will spin forward and everything seems to work.. but if i add a reverse action or a delay the motors will get stock like they will try to work but they wont start and then it works then it stops... im going to try to put a cap 0.1 in the motor connectors tomorrow and see how that goes...