It starts and when I put it in drive it dies

The management light came on and I took it to a garage and their machine reading was that it needed the first coil changed. I did get it changed and then the light went out but came back the next day. Every time I try to start the car it starts and when I put it in drive it dies. When I try starting it again it wont start and the engine management light stays on permanently. When it does start after several attempts, while driving, whenever there is traffic and I have to slow to a standstill, the car shudders. I took it to the garage and now they have said they think it is the fuel injectors. Also it is costing me £20 -£30 per week on petrol.