My check engine light came on my Xb, manual transmission. I took it to the dealer who said there was a little gas in cylinder 3. They cleaned it & said it wasn't sputtering anymore, but it's been 2 days and the engine is sputtering again. It happens in idle, and between 2nd and 3rd gear. I use Sunoco gas regular, only drive @10 miles per day, and do not step on the gas pedal when starting the car. Any ideas?