I loose radiator fliud from rad every week. But cant find out where. Its not coming out the tail pipe or showing on the ground. Took it to 2 dealerships and 1 mechanic no one knows whats going on

Started kangaroo jumping and engine shit down. Started again and as soon as pushed on throttle engine died. Since replaced sensors amd throttle control, idles but revs are up and down and when push on… 

Intermittently kangaroo jumping as though is either fuel starvation,brakes binding,or gears not selecting properly.

Knob on back seat has unsrewed and come of in my hand can't get it back on

When engine is cold it starts but stalls. Even when running it suddenly stalls
Had it checked by Nissan dealer ( Wickham Flower ) they changed 2 sensors no improvement still stalls when cold.