Sluggish 2000 Chevy Silverado?

[wallace_state]

I have a 2000 Chevy and has been running fine, went to turn it on yesterday and it cranked fine but was acting really sluggish, it wouldnt go over 7 or 8 mph. So parked it because I had to get to work. I came home that night cranked it again and it would rev in neutral to about 1200 rpm and then drop down to 200 or so, rev up to 1000-1200 and drop down to 200. What might be the cause of this?

 

[pedro7of9]

nathan has some points BUT befor you go there
1 battery good,,connectiopns clean...low volts makes computer go nuts..iv repaired several with new battery
2 i know but got gas?
3 ever been tuned up..if near 100K and still factory anything get tune..
4 got a distributer cap? moisture gets in and corrodes the rotor...look inside..