cars are my main hobby and photography came along because i wanted some good pics of my stuff. now ive been doing alot of reading on automotive photography and i notice a few things in your shots that could make them better.
first, if you can take your plates off, they can be very distracting. blanking them out looks goofy so dont bother unless you have privacy issues, but remove them all together if you have the time.
second, there is alot of reflections of trees in a couple shots. try to get an area that will cut down on that.
the third thing is a minor detal that may help make a good shot a great shot. in the pic of the wheel, rotate the wheel so that the scion logo is completly parralel with the gound.