i have a 1997 chevy monte carlo 3.1 v6 and i have replaced the idle and throtle sensors but it still wont idle when i start it it revs at 1100 rpm then goes up and down until it dies and it will start right back up and do the samew thing also no check engine light is on.

 

Have you tried checking your EGR valve? Mine is kinda doing the same thing except after it warms up, the idle settles down.

 

yah those are issues sometimes, you can probably clean it out, they even make a new gasket now which looks like the stock one but its got a screen in the center hole...works really well for keeping those things clean