Hey i have a 91 firebird with the 305 tbi. Just replaced, plugs, wires, distributor cap and rotor, checked all vacuum lines and went over the timing and also a new iac. Still idles rough. doesn't stall etc. but then it drives just fine. cant figure it out. thought maybe injectors but it doesnt hesitate when you hit the gas or anything and drives down the road just fine. Any suggestions on what it may be? oh also i did clean the TB as well. Thanks!

 

the nice thing about tbi is you can see if you have any drippy injectors. If you remove the air cleaner assembly and hook up a timing light and aim it at the injector spray pattern this will highlight the injector spray pattern and you can see any dripping.

 

This stuff may help if you haven't done it already
https://www.thirdgen.org/tpimod2

 

Hey thanks i havent tried those yet. I adjusted my idle before my new iac because it was idling like 400 or so in drive so i did it to the 650. Still did it, so i just out the new iac in. did no adjusting etc just undid old in put in new. It idles good until warmed up. someone thought maybe a o2 sensor?

 

Try doing that as described first and then see how it runs