first the engine turns over but won't start ( it starts perfectly in the morning or whenever its parked for many hours), it idles roughly, on June 24th and 25th 2014 it stalled three times while driving. everything just stopped in the middle of the highway without any warning, on June 29, 2014 it started to buck when my foot is on the gas pedal. i also heard a faint whistle sound coming from under the hood and the engine does not throttle smoothly.

things i changed since everything first started back in February 2014: 1) gas pump 2)spark plugs 3) coils 4)change oil and filter 5)change thermo switch 6)flush radiator 7) i also bring it to the mechanic to check for problem code and they did not find anything. i hope that with this information you can provide me with an ides as to what the problem is. thank you