how is the IAC "supposed" to work?

[Turbo Brian]

my car runs like @ss on cold starts (stalls, rough idle, give it some gas and it starts to sputter and sometimes pop under the hood). its getting worse it seems. its a real pain in the butt to drive until its warmed up (pulling into traffic sucks). been doing this since shortly after i got the car a couple years ago.

anyway, i deceided to try and do something about it and it seems the IAC was the place to start. i removed and cleaned it. following the instructions on gnttype, i reset my iac. set the base idle at about 575-600 w/ the iac unplugged as specified. tps is set perfectly at .41 and 4.74. car idles merely "ok" now. i just finished so i dont know how cold start is yet (will know later tonite). im looking at the iac #'s in tlink. its my understanding you want ~20's in park in closed loop. just a bit ago, i got the car into closed loop, iac's were 70's. took a test drive around the block and now iac's are at 8. let it idle for a minute and they are at 0. is that supposed to happen? if it is, when do you want 20's? right after entering closed loop, or after fully warmed up and driven. cuz if i play with the idle screw to bring the iac's up from 0 that will pretty much fubar everything i did when i reset it.

 

[timothydog]

I would say don't try and set your idle RPM. Your chip is going to idle where it wants to idle. More importantly, get your IAC #'s leveled off and let the car idle where it wants once you achieve these. Get it to closed loop and make SMALL adjustments to the throttle set screw pausing for a minute or so inbetween turns to let it level off. This worked for me. If it doesn't work I would suspect a bad IAC motor.

HTH

 

[Turbo Brian]

it seems as the car gets warmer, the iac #'s go down. so i should drive the car around until my iac's are at 0 and then turn the screw till its up to 20's?

oh yeah, cold start tonite still sucked!

 

[V6POWER]

Make sure your A/C is off when checking your IACs.

 

[TurboDave]

Originally posted by Turbo Brian
it seems as the car gets warmer, the iac #'s go down. so i should drive the car around until my iac's are at 0 and then turn the screw till its up to 20's?

oh yeah, cold start tonite still sucked!

That's pretty much the jist of it. Maks small adjustments (1/4 turn or so to watch the result).

Turning the screw CCW will cause the IAC numbers to increase.
If you've had to turn it more than one full turn, it'll be time to re-adjust your idle TPS also.
Takes patience, as they each affect one another.