I have a 2006 chevy equinox 4.3 L V6. It has approx 60K miles. It has been overheating randomly. When it starts up in the morning, it runs very rough and you can smell a fuel smell. I can also hear a rushing water sound when I accelerate. The car does not overheat when driving, only while idol. If you put it in drive and hold the brake on and press the accelerator, the temp immediately drops. The fans are kicking on but not until the car has already shown as overheated. What do you think could be the problem? I have heard a temp sensor, a thermostat, or a blown head gasket. Where should I start?