How exactly do adjust the iac

After several years (yes years) chasing high BLMS I finally got them

Were at 142 at idle, so I finally changed the injectors from the originals to new 30lb injectors
The BLMS dropped to around 137
Next I put a remanf stock MAF and it dropped to 128 to 130, bounces a little.

Noticed the TPS at .50, my IACs were around 18 to 20
Put the TPS back to .42 and noticed the IAC at 0
Does anyone have a pic of what EXACTLY to adjust ?
I see the idle screw on the throttle cable and when I turn
it the idle goes up
the IACS do jump up when I rev it though
I know the TPS and IAC have to be adusted back and forth
I just dont know how to adjust the IAC
Thanks
Steve
 
I must be turning the wrong screw then
That site says

"The IAC function maintains idle quality through commands from the ECM, but, has NO impact beyond the idle range. Idle speed is set by the chip, not by the IAC adjustment screw. Looking at the inside of the throttle body, there are two holes in the lower portion fore and aft of the throttle blade."


When I turn the screw on the throttle cable, the idle goes up. The more I turn the higher the idle goes.
Anyone have a picture for what I should be adjusting
Confused
Steve
 

Fast4Ward

Well-Known Member
mine's a pretty much solid 825. turn the scanner to IAC display, play with the idle screw to raise the IAC #'s once you see around the 10-50 mark ....now change the scanmaster display to TPS and tap to adj for .42
this worked for me great regardless of procedure.
good luck.
 

TurboRegal84

Moderator
Staff member
To reset the IAC you need to turn the screw as indicated below. It is not a fast adjustment. Turn it slightly and let the IAC counts go up or down. Then turn it again slightly. I usually adjust the TPS for every 3 movements of the IAC.

If your IAC counts are at 0 that means the IAC is not being used to control the idle and the idle is being controlled off the too large of an opening of the throttle body from the screw. The throttle blade needs to be closed more to allow the IAC to control the idle. The IAC is a small motor that has a pintle that allows air to by pass the throttle blade...the computer controls this motor.
 

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TurboDave

RIP DAVE
Staff member
TurboBuick.Com Supporter!
this works great for me IAC Reset Procedure i think this is the one your looking for!

,Dan


Unfortunately, that particular procedure is a VERY old and outdated procedure used my GM mechs way back in the early days when they didn't have a scan tool to read IAC available. It seldom achieves the desired results, and often makes things much worse.

The procedure on the Vortex Buicks site is far easier (when a scantool is available) and can achieve whatever IAC value you desire.
 

WH1_T-Type

Well-Known Member
Since adjusting this will cause you to have to adjust the TPS as well....anyone have a good picture like the one above that really shows the exactly what to adjust for the TPS? :)
 

turbo nasty

Turbo Dojo / MNTR
this works great for me IAC Reset Procedure i think this is the one your looking for!

,Dan

Hmmm this still works good for me. Though 500 is too low I go for 650-700 and have no issues.

FWIW- Originally on GN T Type it was the way Joe Lubrant recommended and the original way didnt have 500 rpm ...not sure where that came from.

Dave sorry your wrong :mad:about "outdated procedure used my GM mechs way back in the early days when they didn't have a scan tool that read IAC"

I have the "old" instructions printed off and it clearly states in the instructions to use a scantool and not to go by IAC count but to use RPM. Joe stated clearly in the "old" instructions that he prefers to use RPM vs IAC counts.

Lets get our facts straight here before slamming procedures and such.

Nothing wrong with this procedure other than 500 rpm's being too low.
It's been working on my cars and several other Turbo Regals I have worked on in the last ten years.

Not saying others dont work as well...im just saying.
 

WH1_T-Type

Well-Known Member
Got my IAC set to 22, TPS set to .44 and it has an idle about 775....did all by just adjusting the numbers into the range on my scanmaster. Sounds/runs great!
 

youngstr

Member
The procedure on the Vortex Buicks site is far easier (when a scantool is available) and can achieve whatever IAC value you desire.

Dead on!! used the procedure on Vortex Bucks site, took a whole 10 minutes to set my 85 T, IAC 35 at idle 775 tps .42 so much simpler than the old way! :biggrin:
 

TurboDave

RIP DAVE
Staff member
TurboBuick.Com Supporter!
turbo:

I still stand by my recommendation of using IAC counts vs. RPM.

The RPM method has proven over the years to be problematic for most users.

And why use rpm as a set parameter?? The rpm is specified in "in the chip", therefore setting a comfortable IAC value will always create best results for maintaining the rpm that's in the chip, and NOT in the operators desires. IMHO 650 is too low, and is not a value found in any chips today (unless you're still stuck using a bone stock chip), and 500 is rediculously low. :eek:

You recommend what you think is best, I will continue to recommend what I think is best.
 
Thanks all for the replies
I fiddled back and forth with the IAC and TPS and the IAC is around 12-15 now
Idle around 800 and TPS at .42, but it only goes to around 3.8 volts at WOT
Guess I will have to drill out the TPS holes a little.
But it seems to run much much better
Thanks Steve
 

WH1_T-Type

Well-Known Member
Thanks all for the replies
I fiddled back and forth with the IAC and TPS and the IAC is around 12-15 now
Idle around 800 and TPS at .42, but it only goes to around 3.8 volts at WOT
Guess I will have to drill out the TPS holes a little.
But it seems to run much much better
Thanks Steve

Do you have floor mats in your car?
 
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