when i get in my car in the morning to go to work and start it up it has a real rough idle like it doesnt want to stay running. i usually have to stay in it and pump the throttle a lil til the idle picks up to where it should be. even when i pump the throttle it almost doesnt want to rev up. after that it drives perfect. and it usually only happens in the morning when its like 50 degrees. when i leave work it idles perfect most of the time. its a 2003 gt 5 speed with 35000. what could be the cause?