check injection renualt megane 1.4?

hi my renault megane 1.4 has been having a few problems firstly whlist driving a check injection alert appears and then the revs go high .we have took oit to a couple of gargages and they didn't seem to know what the problem is. secondly my car alarm goes of after i lock the car and we contiune throughout the day untill the car is used again. This car is a nightmare and needs to be sorted garages just want silly amounts of money.