Consider the problem from the dealer's perspective and you'll start understanding how the CPA is applied when it comes to motor vehicles. I've dealt with claims from both sides of the fence so I have some experience of how the process works and how the CPA is applied.
Basically, if you force the dealer's hand, he could (not saying he would) easily claim that in the two weeks you had the car, you drove the car hard/went racing at Killarney/ forgot that the car had more than one forward gear etc etc, failed to check the oil level and suffered the consequences. I imagine you would be hard pressed to prove otherwise.
What do the RMI mechanics say? Are they making mention of latent or patent defects? Did you acknowledge any specific faults on the vehicle when you signed the offer to purchase?