idle problem

[spyderman_21]

someone please help me with some information as i am clueless. I have a 1998 gs spyder 2.4 litre to people that dont know. My car idles as low as 300 then up to 5 then back to 3 while the lights go dim feels like its going to die but doesn't. I have changed the egr valve the o2 sensor and the cat last week. I was thinking it might be the alternator because when i rev it up the lights get brighter but i dont know if then dim cause its such a rough idle so low. can someone please give me some insite before i go blast my mechanic for spending so much money and never fixed the problem.

Any help would be greatly appriciated.

 

[Rob10_99]

sounds like a vaccumm leak to me,
non turbo right?
Check your brake booster lines, it sounds like that thing barely runs.

 

[dsm-onster]

Vacuum leak afte the throttle body or bad Idle Speed Control motor/assembly is likely

BTW you have a 2.0 not a 2.4L.

 

[DSM_Obsession]

im going with vacuum on this or the ISC, i dont think the BIS screw could effect it but its possible