when my car sits for a couple of days, its hard to start . it`ll turn over,but i have to hold the throttle down to keep the car running. This will go on about 5 minutes until it warms up,but then i will rev it up to about 7000 rpm. When the rpm come down to idle it will stay runnin with my foot off the throttle. I also smell alot fuel when this is happening. I have changed the fuel filter,spark plugs, and o2 sensor. help