$A_Money$

i have a 91 rs 305 tbi an I went through the whole thing about settin the idle by the paper clip in the aldl port a and b an waitin 30 seconds for the iac valve to open an then unhookin the iac valve an then go back an remove the paper clip an then go back out under the hood an unhook the est connector then start the car an I got my idle where I wanted it...I hooked the est connector back up an idle goes back to were it was....unplug it an it goes back down...help!!! can I leave it unplugged an run it? will it hurt my performance? what can I do? thanks

Damon

30 seconds ABOVE 2500 RPMS before you unplug the IAC (which you unplug WHILE it's at elevated RPMs). Not at idle. This is from memory. I don't have a shop manual in front of me, so don't quote me on exact procedure. But I recall this is the part of the procedure I always seemed to screw up the first time.

Setting initial throttle opening is something I've found is more easily done just by backing out the throttle set screw until the throttles close completely, then in until the screw just starts to push it open, then a ~1/2 turn further. It's always gotten me PLENTY close without all the gyrations of the factory procedure.

$A_Money$

so ur sayin put the paper clip in the ald connector then start it up an run it up to 2500 rpm then unplug the iac valve?

$A_Money$

bcz I set the idle yesterday by how it says on here an got the idle down to were I wanted it and as soon as I plugged the est connector back up the idle went back to were it was before an if I unplug it it goes down to were I set it

Damon

Yeah, as I recall the procedure, that was the critical step I missed my first time.

End of the day, it was a touchy and, frankly, overly-complex procedure. That's why I came up with my alternate "get it in the ballpark" method, which is very handy when you've adjusted so many things you don't know where you stand any more. Just turn the idle screw all the way out until it stops touching the throttle arm, screw it back in until it just touches and give it another half a turn or so open from there. The ECM and the IAC will raise the idle speed to whatever is called for in the chip programming from there under normal running conditions.

The basic idea is, the throttle should only be physically open enough to hold some arbitrary, very low idle speed, even if the IAC is stuck fully shut. Say, 450 RPMs. Anything above that, is the responsibility of the IAC valve and ECM to provide additional idle airflow to raise the idle speed above that point. Whether that's 1100 RPMs on a first cold-start in the morning or 600 RPMs curb idle, fully warmed up. The airflow through the computer controlled IAC is always IN ADDITION TO the minimum airflow past the throttle plates.

You won't read it that way in a shop manual, but that's how it functions using plain English. Hope that helps.

$A_Money$

that's how my screw is I have it all the way out an its idleing after it warms up it idles at 1250 to 1500 I kno the factory tachs are off but that's wut it shows

$A_Money$

so I need to put the paper clip in the aldl connectors A and B then unplug the est connector then start the car run it up to 2500 rpms then unplug the iac valve then adjust the idle screw?

Damon

Wait, wait. If the idle speed screw (minimum throttle opening screw) is already just about all the way backed out and it's still idling too high, something else is wrong. The IAC only ADDS airflow at idle, as commanded by the ECM, to bring the idle speed UP TO whatever the programming in the chip calls for under various conditions. If yours is sitting at 1100-1200 RPMs fully warmed up, something else is going on. Bad IAC, bad TPS, or something else. Have you looked at this with a scan tool while it's behaving like this?

$A_Money$

Don't have a scan tool only way I can get it too idle down is to unplug the est connector then once I unplug it it idles down to 700 or so in drive