WTF is going on with my ish!!!!

87GNT

Active Member
Nov 17, 2011
297
32
28
Tampa, Florida
Gents-

I just noticed my scan-master IAC numbers on norm temperature, idle is 65!!! when from what I read should be 15-20? . I checked my RPM's and they were at 950 or so....went ahead and pulled back the Idle Air Control Adjustment Screw as far as it can go and the rpms dropped to 850. I understand the RPM's on IDLE should be 500-600.

Are my assessment correct and if so WTH could be causing the IAC to be so high? Also my BLM is 128 which is perfect so no lean condition...its rich as all hell and idles and runs like :poop:

I have a ported 62mm TB and recently replaced the IAC Selenoid about 8 months ago.

Should I check the inner air outlet ??? I did experience oil seepage in my plenum via a stock PCV valve a few weeks ago and since replaced it with a unit sold by RJC.

Any ideas please?
 

1984 t-type

Murphy's Law
Jul 11, 2010
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I think 500-600 would be kind of low mines warmed up idles around 800-900 i think and thats with a TT chip. Whats your TPS reading at ? Whenever you adjust your IAC it changes the TPS
 
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jasjamz

THS Racer
Sep 30, 2004
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To lower the IAC you need to drive the screw in or clockwise. Then lower the TPS voltage by tapping the sensor end downward.

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dank GN

BlackArts Automotive (661)993-8277
Jan 11, 2009
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I have never seen a turbo Buick idling at 5-600 rpm that’s super low imo I’ve always seen them shooting for 850ish . Adjust your IAC then go back and adjust your tps to .40-.44 and you should be good
 

ScottHeidinger

Active Member
May 2, 2015
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northeast Florida
make sure your AC is off.
Is this a requirement? I never read that anywhere before but thank you if t is.
Yes u want to set it with ac off. I set it with the ac on once and it would idle at 1000 rpm even with the iac at 0 with the ac off. Had to reset it with the ac off to get the idle back down to 800.


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earlbrown

runs with scissors
May 26, 2001
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lagrange, GA
Thats my issue....I had it at 850 and my IAC reading is still 65
You're misunderstanding what the IAC actually means. The number isn't a setting, it's a side effect.

For the engine to idle at what the chip wants, the engine needs ''X'' amount of air. The ECM uses the IAC motor to get the airflow up to the required amount. If the throttle blade is almost shut, then the IAC has to open quite a lot to let the engine idle (and might have an off-idle cough). If the blade is open too far, the IAC will shut completely off and read 0.

The trick is to open the throttle blade just shy of what the engine needs so the IAC can make up the rest.


Keep in mind, screwing with the throttle blade will alter the TPS reading too. So those will have to be adjusted back and forth until they both read good numbers.
 
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