My 91 rs with the stock 305 will not idle correctly. It will slowly com back to about 1000 rpms which I know is to high. I have adjusted the idle per the chilten manual and still no success. I have rebuilt the tbi unit, new thermostat, coolant temp sensor, tps switch, egr valve, o2 senser, new injectors, new iac valve, and even new computer! Any suggestions would be appreciated.

 

how do you do this. to my knowledge there is no idle adjustment on a TBI it is computer controlled.
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did you check all of your vacuum lines? it sounds like a vacuum leak.

 

Your're correct, the computer does control idle. But in the chilten manual there is a step for adjusting the idle only when a replacement tbi is installed. First remove idle stop screw plug or cap, groung diagnostic connector, turn ignition on wait 45 seconds do not start engine, disconnect idle air control valve with ignition on, remove ground from diagnostic connector and disconnect distributor set timing connector, connect tach to engine, place in park or nuetral if a manual trans, run engine till operating temp ia reached, now adjust idle stop screw to get 450-500 rpm. Turn engine off and reconect iac, distributor and cover idle stop screw with rtv.

 

I just learned something. I read an IAC adjustment tech article on here but i don't think it is quite that detailed and you just used a lot less words. anyway it is pretty close. I am no expert but there are many things that come to mind. you said you replaced the computer, is the prom the right one for your vehicle. it is possible that something may be off in the settings there or it could be a simple vaccum leak. if you have a laptop you can buy a cable and download some free software that will help diagnose your issues. i am just learning about some of this on these boards. also i have noticed that a lot of the things we ask on here have already been covered in a previous post and you can find a lot of info by doing simple searches on here.