Engine Performance problem
2005 GMC Yukon V8 Two Wheel Drive Automatic 53000 miles
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HI

My engine light is on. I took to a mechanic and can not find anything wrong. He thinks it is the sensor in the gas cap. Now I have to press the gas pedal to keep it from dragging when it starts. Does it have anything to do with the Ethanol in the gas. I do not think I have a fuel filter. Is it maybe the sensor and how diffacult is it to replace?

I had the fuel ejectors clean last week at Grease Monkey and the light stayed off until I started it up again. Why?

Thanks Rlanier