There is a lot to learn about editing and processing images whether it be in photoshop, lightroom, or whatever other editing software you may have, it takes times and practice, but the key to good results always starts with the camera.
I would start off looking at the way you take your pictures, think about the composition, the background, the lighting and more important think about what you expect the end result to look like.
Study other peoples photography and look at what makes it stand out, where the subject is in the frame, Learn about the rule of thirds and how to position your subject.
The Subaru shot for example looks a little snapshot-ish, I can understand including something else in the frame to turn it into a scene, but the tree trunk just looks bizzare, and the car is too far away for it to be the main subject, we know it is, but the picture doesn't tell us this. I don't think the high ground behind does anything for the shot either, For my money i would have shot this with an open background or from a lower angle to include some sky in the shot.
Car shots also work better when you apply the rule of thirds and give the car room to move in the frame, If the car is facing left like this then position it towards the right of the frame and visa versa. hope this helps.