[needalotofhelp]

Hi I've read a lot of the post and have seen some similiar problems as mine,but not quite the same. Here's my problem:

When driving down the road as I press on the gas, my car shutters something terrible. If I let off the gas for a second or put more pressure on the gas peddle the shuttering stops. You can feel and hear something rumbling under the gas peddle on the front underside of the car. When it acts this way while idling it runs really rough like its not running on all cylinders. On my way to work this morning, it was 40 degrees out and I had to be off the gas on the gas the whole way to work, when I stopped at a stop light the engine was running rough, almost like it was going to stall. At lunchtime, I went out to drive it around so I could describe how it runs...well, it ran smooth as silk. No shuttering going down the road and at stop signs it purred like a kitten. The only thing I noticed was when I first started it and stopped at a stop sign, the engine kinda hiccupped, just once and then it was fine. It is now 75 degrees out, and I've never associated the problem with the temperature but the problem, but It will run awful for a while and then seem to work itself out, much like today.

Anyone else having this problem? If anyone has any ideas as to what could be causing this, I would greatly appreciate some insight.