So I decided to set my TPS

[turbo2nr]

TPS .42-.46 and WOT should be at or just over 4.0
IAC numbers should be from 1-20

TPS is more important tho. Dont get hung up on the IAC numbers.

I do not think is that simple.

Car needs to be at what coolant temp when you say IAC @ 1-20?

Outside temp is what? The cooler the ambient, then the lower the IAC of course....

Really Hot outside and low atmospheric pressure, then it will be above 20, no?


Car in Park or Drive?

etc etc...

 

[TurboDave]

I got it set in no time. My TPS is 42 and 4.61 at WOT. My IAC is now at 12 at idle. IAC does not got to zero when I drive over 40 mph? Why is that?

I still have a slight hesitation at light throttle cruise speed say 45 to 70 mph. Kind of feels like the car is surging a hair. My afr is lean, 14.8 to 15.5 ish. I'm limping by on the 5.7 chip I had burned for this motor when I ran the champion irons. The only thing I changed was the better flowing TA aluminum heads. Wouldn't think that would matter but maybe it does. I'll be changing to SD2 next week.

Any ideas on the surging? It's real real slight but it's there. If I throttle is a bit it's fine

You need not worry about what the iac is reading when not at idle. It's an idle air controller, not a cruise air controller.

 

[BARRACUDA1968]

Ok wasn't sure? I'm a carburetor guy, I can tune a holley like you guys can tune these cars. On a Holley at cruise speed you're still on the idles circuits so jetting is irrelevant like most people think. I'll keep learning.

 

[TT/Ameasap]

I do not think is that simple.

Car needs to be at what coolant temp when you say IAC @ 1-20?

Outside temp is what? The cooler the ambient, then the lower the IAC of course....

Really Hot outside and low atmospheric pressure, then it will be above 20, no?


Car in Park or Drive?

etc etc...

This is exactly what I mean by "Hung up" on IAC numbers.

 

[BEATAV8]

You need not worry about what the iac is reading when not at idle. It's an idle air controller, not a cruise air controller.

Yes that's very true, but the ECM needs to fully close the IAC and co-ordinate that position with 0 IAC counts. It does that calibration when vehicle speed is over 35. I learned all about that little feature when my buddy drove around with a broken speedometer cable for a few days and was asking me why his idle speed was getting higher and higher each day.

 

[TurboDave]

Yes that's very true, but the ECM needs to fully close the IAC and co-ordinate that position with 0 IAC counts. It does that calibration when vehicle speed is over 35. I learned all about that little feature when my buddy drove around with a broken speedometer cable for a few days and was asking me why his idle speed was getting higher and higher each day.

Odd, I have not found that to be the case on either of my GN's. And they both have absolutely PERFECT street manners, as well as WOT, and I've NEVER seen my IAC numbers go to zero under any circumstances (unless I mis-adjusted them to to so at idle).

Try as I may, I've looked through a couple of my many chip files and have not been able to find anything in them that commands what you're saying the IAC should do. In particular, nothign to do with speed or rpm.

 

[Ttype6]

Every time the ignition is turned off and on,the IAC re-sets to zero. If anyone wants to test this,they can remove the IAC and push it all the way in or pull it out and re install it,plug it back in,and turn the key on then off and then start the car. It will start in the same fashion that you are used to because this scenario takes place every time you turn the ignition off and back on.The computer counts from zero to open it to a certain amount during the next fire up to achieve a certain amount of airflow around the throttle blade. The amount that the computer decides to open the IAC during start up is based mainly on coolant temp. From there,the computer opens or closes it controlling the amount of air that is allowed to flow around the throttle valve to maintain a certain idle rpm.

 

[TurboDave]

Every time the ignition is turned off and on,the IAC re-sets to zero. If anyone wants to test this,they can remove the IAC and push it all the way in or pull it out and re install it,plug it back in,and turn the key on then off and then start the car. It will start in the same fashion that you are used to because this scenario takes place every time you turn the ignition off and back on.The computer counts from zero to open it to a certain amount during the next fire up to achieve a certain amount of airflow around the throttle blade. The amount that the computer decides to open the IAC during start up is based mainly on coolant temp. From there,the computer opens or closes it controlling the amount of air that is allowed to flow around the throttle valve to maintain a certain idle rpm.

IIRC the IAC key on commanded by the chip for cranking is 150. Try it, turn your key to on, and check the IAC value on your scan tool before cranking.

 

[Ttype6]

IIRC the IAC key on commanded by the chip for cranking is 150. Try it, turn your key to on, and check the IAC value on your scan tool before cranking.

What does 150 mean?
How does the computer know that the IAC is in the commanded position?

 

[BEATAV8]

It's been quite a while but I do recall watching the IAC do this "zero calibration" when I was cruising or decelerating from highway speeds.

If you google stuff like "IAC and VSS fault" or "idle speed with VSS fault" you'll come up with some references for it.

 

[BEATAV8]

here's a few refs:
http://www.gmtuners.com/tech/TPS_IAC.htm

http://www.pontiacperformance.net/techarticles/osg/ECM.html

 

[1952ray]

IIRC the IAC key on commanded by the chip for cranking is 150. Try it, turn your key to on, and check the IAC value on your scan tool before cranking.

Yup, just tried mine. It shows 150