There is a setup for the IAC that MUST be done if you want to get it right the first time. I don't have the factory manual with right now but there is a VERY specific order you have to do things. First you must set the seating flange to pintle tip distance to as I recall 28mm. This the base setting for the IAC, if its not there when you do the rest it gets hit and miss very fast. After that there was a sequence of like turn on the key to run but don't crank the motor with the IAC unplugged. Then turn off the key and plug the IAC in. Then turn it back etc.

The factory manual has a whole page as I recall on just getting this thing correctly installed and calibrated with the computer to make it work right. Might be worth the trouble to try to get the info. Consensus with my friends who were too lazy to take the IAC out again to set the pintle distance was that you can wing it a few times and sooner or later you will get close enough to make it work ok. But if you want dead perfect you will probably want to do the factory method.

 

This about sums it up, so

 

Once again!!
89 Minimum idle set

 

[QUOTE=corvette1989bham]Since I hate it when people get a problem fixed after asking for other peoples help and NOT posting what the fix was here it is:
Turns out (embarrassed) I didnt unplug the IAC when setting the minimum idle. I had a brain fart and unplugged the TPS instead(I know MUCH better). :o
Thanks Again

[QUOTE=MR MOJO]This about sums it up, so

I hope you don't mind me adding this MR MOJO, but this is what its all about. "No need to be embarrassed" Even the best of the best make silly or major mistakes, if they never have then they would not be the best. Even the worst info can come in handy at times, reading a repair manual and turning a wrench are two different games.

Happy New Year!

 

There is some interesting stuff here. Since my procedure differs slightly from that of Lars mostly excellent article and as has already been noted, there was some info posted that was not quite as correct as it should have been, I'll quote directly from my GM 1988 Factory Servcie Manual page 6E3-C2-12 & 13 - Minimum Idle Speed Adjustment.
-----
"Before checking minimum idle speed, be sure ignition timing is correct and, before making any idle speed adjustments, be sure throttle body is clean around the throttle plates.

Adjust
1. Pierce the idle stop screw plug (15) with an awl, and apply leverage to remove it.
2. Adjust idle stop screw assembly (16) as required.
3. With IAC motor disconnected, ground diagnostc terminal.
4. Turn "ON" ignition, do not start engine. Wait at least 30 seconds.
5. With ignition "ON", disonnect IAC electrical connector.

Important
6. Disconnect the distributor set-timing connector.
7. Start engine and allow to go "closed Loop".
8. Remove ground from diagnostic termainal.
9. Adjust idle stop screw to 450 rpm in neutral for manual or automatic transmission vehicles.
10. Turn ignition "OFF" and reconnect connector at IAC motor.
11. Adjust TPS if necesssary: ...
12. Start engine and inspect for proper idle operation."
-----

Based soley upon the info in the 1988 FSM, (since earlier/later model year GM manuals may differ), it is obvious to me that the FSM procedure starts with a cold engine, but does not actually attempt to SET the minimum idle speed until the engine is warmed up to "Closed Loop" status. It would seem to me that starting with an already warm engine would have no undue side effects and would be easier to do if you already have a significant idle problem that disconnecting the IAC would magnify.

The other manuals my differ, but in my 1988 FSM the procedure calls for both manual and auto tranny cars to be in neutral, and to use 450 rpm as the base idle.

This is close, but not completely correct. As EFI-CFI has already stated, there is no periodic need to reset the IAC. The procedure you refer to deals with the INITIAL setting of the IAC when a new one is first installed. It should not be an issue with an already working IAC. From the 1988 FSM page 6E-C2-4:
-----
"If the IAC valve is disconnected and reconnected with the engine running, the idle rpm may be wrong. In this case, the IAC valve can be reset by starting the engine momentarily and then turning the ignition "OFF". When servicing the IAC, it should only be disconnected or connected with the ignition "OFF". This will keep from having to reset the IAC."
-----

The procedure Jaxian referred to, for a new IAC at initial install, 1988 FSM page 6E-C2-13:
-----
"Before installing new idle air control valve assembly, the position of its pintle MUST be checked."
...
Measure
Distance from gasket mounting surface of IAC valve to tip of pintle.
... If distance is greater than 28mm (1 1/8in.) reduce it as follows:"
----
The reason you must have 28mm clearance when installing an IAC is so that it won't be jammed against the valve seat when first installed, which could damage the sensitive IAC stepper motor.

Your mileage may vary.

 

Once AGAIN? When did you say that the first time? What does it mean? Does that have something to do with justifying setting the minimum air adjustment on a cold engine?

vetster86,
You may be talking about two different things. At least your terminology makes me think you are talking about one thing, but now it seems your words indicate you are talking about another. There is a procedure for "setting" the IAC upon installation that Jaxian goes into detail explaining. He says, "There is a setup for the IAC that MUST be done if you want to get it right the first time", and goes on to explain the steps in setting up a freshly installed IAC. The procedure he explains allows the ECM and the IAC to get into "sync". They would get there, eventually on their own, but this facilitates the process. What Jaxian explains, is ONLY for the installation or re installation of the IAC, despite what else he says.

When setting the minimum air adjustment (not idle speed, or minimum idle) the IAC must be taken out of the picture. Only air passing the throttle plates is to be adjusted. With the ignition, "ON" and the ECM in the diagnostic mode, the IAC closes. The ECM fully extends the pintle to close the IAC passage. This is not normally referred to to as "setting the IAC". After the ECM has been in the diagnostic mode, with the ignition "ON" for 30 seconds or so, giving the IAC the plenty of time to close, the IAC is unplugged, to prevent the ECM from opening the IAC when the car is started. NOW, with the IAC closed, the only air that can enter the engine is via the opening at the throttle plates. The spec for "minimum air" is an abnormally low idle speed, solely for the purpose of set up. The actual idle speed is burned into the prom and controlled buy the ECM manipulating the IAC. The actual idle speed is not "user adjustable", at least not from under the hood. Maybe that helps clear up a few points.

RACE ON!!!

 

Great stuff, there. You posted that while I was still typing. Yes, I'm a slow typer. About my only comment has to do with step "3.". I hope that is a typo, and that the IAC motor remains connected, while the diagnostic terminal is grounded. Otherwise, not only won't it work, step "5." is superfluous.

RACE ON!!

 

I hate when I forget to hit the "close" button