I drive a doge neon 04. If I am driving and I press the gas pedal lightly the car drives with no problem, but the minute I "mash down" or press it a little harder the car jerks/sputters. The car does not cut out so it is not a blocked catalyst and I changed the mass air flow sensor and it didnt do this for a day and then started back again. The car also gives a hard start I must turn over the engine for a long time before it starts. COuld you please help and point me in the right direction. I hooked it up to a computer and the only code was p0440 and that is loose gas cap or i put gas with the car on.