2005 Dodge Neon Smell Prominent Gas While Car Idling Checked There Leakage

What to do if I smell a prominent gas smell while my car is idling? I have checked and there is no leakage. I tried to replace the camshaft sensor but found that there was too much to it so I put the screw back in and cranked up my car. Thirty seconds after cranking the car, I could smell the gas.