I don't know if this is the right place to post but I really hope someone can help.

My boyfriend owns a Ford Mondeo Estate TDCI and it is nothing but trouble. We had a failed Injector in the engine and we had it replaced at a local garage at a cost of almost £300. When we got the car back boyfriend noticed that oil/fuel was leaking from the Injector and over the engine cover. Car went back to garage and they said they replaced seals. We checked the car again about a week later and the Injector was still leaking. Car went back to garage again, they had it for several days before we got it back but it was still leaking and we noticed that there was steam coming out from under the bonnet when we stopped. We took the car back again and the garage told us that the Injector they replaced is a modified Injector and needed Modified seals so they had the car for several days again and we collected it last week. They have indeed replaced the seal but they have used some kind of sealant around the Injector seal.

Since we got the car back it is now running lumpy, struggling to accelerate and kicking out black smoke from the exhaust. It did non of this when the Injector was leaking. We are very worried what the garage has done to the car and really have no idea what to do next. We can't afford to take it to another garage for repair.

Can anyone help?