I have a 2003 Ranger with 40,000 miles. Started it up this morning and the idle was extremely fast. After about a minute it returned to normal, but when I started driving I noticed that when I give it gas, the engine hesitates and engine speed does not increase. If I take my foot of the gas, the truck speed will increase to 40 miles per hour. Giving more gas makes the truck hesitate and it seems like it will stall. Suggestions?