Alrighty... first off your photos don't turn out the way you imagine them or like the ones on this thread for a few technical reasons.
1) You choose horrible places to photograph them. In a parking lot beside other cars is hardly a place to photograph.
2) Your choice of in camera crop points. Some photos cut off the bottom of the wheel. Some photos you cut off the front end of the car.
3) Utilizing your aperatures will help your photographs. If you are on Auto or Program the camera is likely to choose an f-stop around 5.6 or 8. Given your lens focal length you should be able to extract some decent bokeh on it. If you want to create that depth of field with your particular lens you are likely going to have to shoot at full zoom with the absolutely lowest f-stop possible (f 4 is what I'm guessing your lens is). This will start to create the depth of field that you see with many photos like Domani or MikeJo photograph
4) Sharpen your photos using Unsharp Mask. There are many threads and websites that show you how to do this. But sharpening your photos will make for a more striking picture.
5) In the thread you complain that it is overcast day. In fact, it's probably the best condition to photograph. The shadows aren't as harsh and the colours are richer.
All in all, it would better serve you to look at magazines such as Performance Auto and Sound or Import Tuner and look at the photos. Study the compositions (not the women) and try to photograph vehicles in the same way. As you get better, break off from the common shots and start creating your own ideas.
Don't stop shooting. Everything comes with practice. Post what you shoot so others can help you learn. Hope this was helpfu.