APM is armed but no control of throttle

my APM is armed but as i start to rise my throttle motor starts spin and suddenly all motor stopps and moving thorttle up and down does not make my motor spins … but as i switched on my channel 6 (stablize mode) than all motor start spin if i move throttle up and down motor work perfectly so why this strange behavious… why my motors are stopping after running for 4 to 5 second and why it is working only in stablize mode