I just purchased a car 4 days ago and now it's starting to rev up when i'm at a light or idling (sitting in taffic) It doesn't do I much but it does it enough for me to notice it. It's drives fine it only accures when I idling. I had the alternator, starter and battery tested and it came back fine. I had the oil changed and the mechanic said I had a very small oil and transmission leak. I was only enough to make the pan wet. Please help. Did I buy a lemon?