What is wrong with my 2012 LR4?

[Lovemyrov]

I have a 2012 Landrover LR4 & about 3 weeks ago my, brakes worn, light comes on. I had 26,000 miles on car. Take car in & they have to change brakes & rotors. They also changed my oil. I go to pick car up, drive about a block away to get gas, put car in park & it begins shaking. Almost like it was going to die. It has never done this before. I took it right back to them. They were closing and said that they could look at the next week. They offered to give me back loaner & keep my car but with the 4th of July holiday I chose to just drive my car home as they said it would be fine & they would look at next week. Car continued to act funny. Did find out that it shakes bad only when air is on. Again, it has never done this before! I would know because I sit in my parked car with air on daily, waiting on kids, etc. I started it one day & black smoke started blowing out the back of car. They took car yesterday & said nothing is wrong at all, but the shaking is still there. They said the shaking is just the air compressor. Also does it some when you first accelerate. Something is wrong but I have no idea what it is. They just look at me & probably laugh when I leave but something is way off with this car!! You don't pay this much for a car for it to shake like an old Chevy truck!! It never did before. Ever. Anybody have any ideas?