I'm new to this forum so if the question has been posted, please bear with me. I have a '99 S-10 LS 4x4 stick shift truck (with 60,000 miles) that has been doing strange things in the last couple of days. First, when I try to start the engine it cranks as if the battery is going death, then when it starts, it revs up by itself all the way to 3,000 rpms. To bring the rpms down I'll have to take off and stop several times, and when they go down and I try to get going again, I have to press the gas pedal halfway to get the truck moving to the point where you can hear the valves knocking as if it was lacking power. What could this be?