Alright so I got this Scion xD as well as my Mitsubishi Eclipse. This new problem I have is that my check engine light comes on for some reason and the car likes to jerk forward from first gear into second when normally it would be a smooth transition. Also, my VSC off symbol comes on resulting in no traction control. I have some knowledge about repairing an EVAP leak or replacing the seal on the gas cap, but I'm not sure how I would be able to do it, it honestly sounds better than actually doing it. I'm just looking to see if it is either an EVAP leak or an engine vacuum leak as I don't hear a hissing noise coming from the engine, but my VSC off symbol comes on so I'm not sure what it is, but I've pinpointed it down to these two issues. What do you guys think?

 

Have you plugged in an OBD-2 reset unit yet? That will tell you what the fault is. Why do you think that a gas cap is the issue? Sound more like a speed sensor issue to me....