Just wanted everyone who tried to help me know that my engine now idles with only a 20-30 rpm fluctuation. Thanks to ski_dwn_it for putting up with me for the last three days. He instructed me how to set the idle a totally different way and it is idling just fine now.
If I ever get a day without snow all over I might even get to take it for a ride. Thanks Jesse.

 

 

Do you have the instructions to post here?

Thanks

 

The procedure is for modded cars only, is yours modded? I don't think Jesse would mind since he said he's posted it many times, it should be made a sticky but that's another story. If your car is stock and the minimum air idle procedure doesn't fix the idle then you have other problems. Let me know what your mods are and I'll see if Jesse's info will help you, then I will post the instructions.

 

Glad you got it under control.

I set my own idle in a similar fashion to what Jesse has previously described.

Basically, I set the min air to equal my warm target rpm. In my case, that is currently 850 rpm. When the car is warm, it will idle at 850 rpm and maybe 0-10 IAC counts depending upon the outside air. In this manner, the IAC can never reduce the rpm much below the target rpm.

Now I have the full range of IAC to add idle rpm if desired. This can be useful.

I use this extra rpm capacity as a sort of pseudo launch control feature. I can now command a 2000 rpm idle with the A/C add function (+1150 rpm) and my car will rev up to 2000 rpm on the IAC and be ready for launch (if the A/C compressor is disconnected).

I've also played with the IAC gains to speed up the effect. It takes about 1-2 seconds to rev-up now when I hit the button.

So I've set the throttle stop and tps and IAC to support the max idle possible and then worked backwards to meet my 850 target rpm with near 0 IAC counts.

All the other relevant parameters in the chip have been tuned to match, so it works well under all conditions.

 

I want to thank you for your help too, I was trying to set my idle the way GM does for stock vehicles and as you know it just don't work on modded engines.

 

Please post this procedure. I have a fluctuating idle that I cannot fix following GM instructions. I have a 350/superram/219 cam/ dart pro1 heads,ect. Thanks

 

Okay, I got the go ahead from Jesse, this is no big secret but it's his info I'm passing on. Make sure and thank him if it works for you. Remember, you have to know what your chip is programmed for your idle.
First thing is to cross the AB terminals in the diagnostic port, paper clip or however you prefer to do it. Turn the key on, the cooling fan will come on, wait at least 30 seconds then disconnect the IAC. Take the paperclip or what ever method you used out of the diagnostic port and start the engine. Lets say your chip is programmed for an 800 idle, set the idle to 700-750. I then shut the engine off and reset the TPS to
.54-.56 volts. Reconnect the IAC and start it up you should have a nice even idle at that point. My engine only fluctuates 20-30 rpm. Keep in mind that if this does not work you have something else wrong. Factory stock engines can be set the way GM describes.
Then when you are celebrating your victory over that darn idle remember to thank Jesse (ski_dwn_it)

 

Ahhh glad this is helping some people. The KEY is to remember the IAC is only there to assist in SMALL variations or deviation from your BASE idle. For example, when you go from park to in gear, the IAC will open a bit to maintain a given idle. Remember the IAC is just a controlled vacuum leak! Or when your AC kicks on it will add ~50rpms. Things like this.

Where you guys get into trouble is when you mod your car up and these mods require your BASE idle to be raised for the motor to run smoothly. When is the last time you saw a high HP motor idle at 600rpms? Mine idles at 1100 for reference.

As described MANY times the stock way to set the idle is to set it at some very low value, like 600rpms....with this setting the IAC will be needed to raise the idle another 200 or more RPM if the chip is programmed at say 850rpm. This is WAY Too much.

Long story short is you want to set the idle (using TB screw) with to just under the desired idle...then let the IAC pick up the other 50 or so RPM....this is a nice amount for the iAC to handle. IF you get over 100 rpms the car will hunt for idle due to the variations in the incoming airflow - so the IAC will fight itself trying to open and close and it just can't move that fast.

The IAC is an "assist" type device...its not intended to compensate for large deviations from set idle points. I ran my 434 for 2 year without the IAC even being on the car. Just set the idle at 1100 with the TB and it purred like a kitten; well a ****-ed off one anyways. since hooked it back up to do some playing around and stuff, but you wanna keep that IAC under control and not let it have too much to do with the required idle airflow...otherwise you WILL have idle problems.