The car runs fine when on the gas but is constantly not maitaining idle when the cluth is pressed or if I throw into neutral, causing me to rev so the car doesnt stall out. Also when I hit a speed bump or something and the car is in neutral, the hit causes the car to drop idle again.....IM LOST. You can also smell a faint exhaust'ish/gas'ish smell when coming to a stop...sometimes. My only thought is maybe the O2 sensor??

Id like to hear opinions on what this "could" be. Thanks in advance.