What is wrong with my car cmax tdci

[Amivwilson]

Hello

hoping for some advice. Bought second hand cmax a year ago, it misfires when it wants to. I have had it in with Ford twice, they felt it but they could not diagnose. I have had one major misfire and had to have an injector replaced but it still misfires. 

Now the car is shaking, I have had all the tyres replaced and balance n tracking done but it is still shaking :( Aldo when I start the car and at low speed there is this whiring noise that started this morning :( 

i cant afford a new car and only had this a year so really would love to know what I have to repair! 

Thanks