Vauxhall Zafira cutting out

hi there, 12mths ago i took car to the garage because as i was driving and dropped gear the car dyed and all the lights came on,this happened tree times in one week b4 i took it garage. they changed my egr valve,got the carback everything was fine for a coulple of weeks then it happened again,this time i noticed a little white smoke from my exhaust and everytime i turned the key to start the car there was a tick tick noise b4 the engine started.so i took it back to the garage,4 times they changed that egr valve,until i asked for a full check on the car.i have 4 kids the car is my lifeline.i have had apart from the 4 egr valves,a new battery and alternator,new middle and rear exhaust and a fair few other things.i foned the garage again today as it is happeneing again and they told me they cant find the problem.sumone pls help,i feel like scrapping the car its getting to me that much but i need it and cant afford to buy a new car.