IAC count ?
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From: Troy, AL
Re: IAC count ? That's not good. You should set a code like that before long.
Make sure you're looking at the "IAC Pintel Position Counts". That may vary between different versions of Autotap, not sure.
About 25-35 is good for a heads/cam engine with the car fully warmed up. I point this out because they will generally be lower once the engine is fully warmed.
Did you drill the TB hole too large? Vacuum leak perhaps?
Make sure you're looking at the "IAC Pintel Position Counts". That may vary between different versions of Autotap, not sure.
About 25-35 is good for a heads/cam engine with the car fully warmed up. I point this out because they will generally be lower once the engine is fully warmed.
Did you drill the TB hole too large? Vacuum leak perhaps?
Re: IAC count ? Well i just got back and i think mine is bad. I was checking the IAC Pintle Motor POS. It stays at the 0 count cold and after warmup. I even disconnected the motor while the engine was running and no change and no code. What exactly is the function of this thing? The only thing that happens to my car on start up is it stumbles slightly, but usually it finds the idle after 1-3 surges. By the way this count of 0 has been there for a while. I haven't drillled the throtle, but it is a MMS ported TB and it's been on for almost two years now.The car has the hammer cam, flps, LS6 intake, stock heads
[ February 11, 2002: Message edited by: Dean ]</p>
[ February 11, 2002: Message edited by: Dean ]</p>
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From: Barbaria
Re: IAC count ? This makes me worried. I have a stock motor 98 LS1, stock TB and my IAC counts are between 0 and 3 at idle...no related SES lights. When I first turn the car on its at 60 or 70 and does a countdown...gets stuck around 25-30 for a while...then counts down again to 0. I don't get it...my car runs awesome.
Anybody know?
Anybody know?
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From: Troy, AL
Re: IAC count ? The IAC controls the idle rpm. It has a plunger (pintel) that pulls in and out to control the amount of airflow at idle.
If it stops working you'll know it. Your idle won't be exactly the same at all times. I don't know why it would read 0 and still be working. Something is strange there.
Unplug it an leave it unplugged. You'll see what I mean. If you just unplug it with the engine fully warmed you will likely notice little difference (except for the code that you will soon get) since the pintel will freeze in whatever position it is in at the time. Let the car fully cool and start it back up with the IAC still unplugged and frozen in it's fully warmed position and see what happens.
Or, as a quicker experiment, hold the throttle open at say, 3500 rpm, and disconnect it. See where you idle is when you release your throttle. <img src="gr_stretch.gif" border="0">
If it stops working you'll know it. Your idle won't be exactly the same at all times. I don't know why it would read 0 and still be working. Something is strange there.
Unplug it an leave it unplugged. You'll see what I mean. If you just unplug it with the engine fully warmed you will likely notice little difference (except for the code that you will soon get) since the pintel will freeze in whatever position it is in at the time. Let the car fully cool and start it back up with the IAC still unplugged and frozen in it's fully warmed position and see what happens.
Or, as a quicker experiment, hold the throttle open at say, 3500 rpm, and disconnect it. See where you idle is when you release your throttle. <img src="gr_stretch.gif" border="0">
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Re: IAC count ? The (puter) IAC thinks it's Lean at idle so it 'cuts off air' to richen up the gas. '0' mean lean condition. Vac leak or a lean condition'. hope this helps. <img src="gr_stretch.gif" border="0">
[ February 12, 2002: Message edited by: zombiedude ]</p>
[ February 12, 2002: Message edited by: zombiedude ]</p>
Re: IAC count ? Here is something you can try. <img src="gr_images/icons/wink.gif" border="0">
http://members.fbody.com/RCowan99SSConv/stepper.html
http://members.fbody.com/RCowan99SSConv/stepper.html
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From: Troy, AL
Re: IAC count ? I agree, it can be a good indication of a vacuum leak (but it can also indicate a TB hole drilled too big or a TB blade that isn't closed enough) but it's not necessarily indicating an actual lean condition. In the case of a vacuum leak, if the O2s are still staying around .450mv (they of course jump back and forth) then there is no lean condition and the reason there is no lean condition is not because of what the pintel is doing. It's because the O2 sensors are correcting for what would be a lean condition.
"The (puter) IAC thinks it's Lean at idle so it 'cuts off air' to richen up the gas."
I understand what you're saying but it's just a little misleading. <img src="gr_stretch.gif" border="0"> This statement sounds to me as if the PCM uses the IAC to richen up the mixture. It doesn't.
[ February 13, 2002: Message edited by: Colonel ]</p>
"The (puter) IAC thinks it's Lean at idle so it 'cuts off air' to richen up the gas."
I understand what you're saying but it's just a little misleading. <img src="gr_stretch.gif" border="0"> This statement sounds to me as if the PCM uses the IAC to richen up the mixture. It doesn't.
[ February 13, 2002: Message edited by: Colonel ]</p>
Launching!
Joined: Nov 2001
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From: Minneapolis, MN
Re: IAC count ? on a basically stock motor, what should the IAC counts be at at idle? what about cruising at different RPM's, and full throttle? How is the IAC related to the TPS? I'm trying to figure out this problem. https://ls1tech.com/ubb/cgi-bin/ulti...c&f=1&t=000227
Re: IAC count ? Since it's a MMS ported throttle body and probably somebody else's core return, do you think it's possible the butterfly hole may have been drilled out by someone else prior to you buying it...
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From: Troy, AL
Re: IAC count ? [quote]Originally posted by Red02LS1:
<strong>on a basically stock motor, what should the IAC counts be at at idle? what about cruising at different RPM's, and full throttle? How is the IAC related to the TPS? I'm trying to figure out this problem. https://ls1tech.com/ubb/cgi-bin/ulti...c&f=1&t=000227</strong><hr></blockquote>
On a basically stock motor the IAC will probably be in the 60-90 range (depends on several things.) It's not that crucial on a stock engine since the idle is very stable to begin with.
During cruise and WOT it doesn't matter where the AIC is since you're not at idle. That is the only job that the IAC has...maintaining the idle RPM that the PCM commands. You'll notice that the IAC pintel position goes really high at anything other than idle. Why? It's just getting into position for when you suddenly wack the throttle closed (so it doesn't have to play catch up when the manifold pressure drops so suddenly.) <img src="gr_stretch.gif" border="0">
<strong>on a basically stock motor, what should the IAC counts be at at idle? what about cruising at different RPM's, and full throttle? How is the IAC related to the TPS? I'm trying to figure out this problem. https://ls1tech.com/ubb/cgi-bin/ulti...c&f=1&t=000227</strong><hr></blockquote>
On a basically stock motor the IAC will probably be in the 60-90 range (depends on several things.) It's not that crucial on a stock engine since the idle is very stable to begin with.
During cruise and WOT it doesn't matter where the AIC is since you're not at idle. That is the only job that the IAC has...maintaining the idle RPM that the PCM commands. You'll notice that the IAC pintel position goes really high at anything other than idle. Why? It's just getting into position for when you suddenly wack the throttle closed (so it doesn't have to play catch up when the manifold pressure drops so suddenly.) <img src="gr_stretch.gif" border="0">
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From: Lake Orion, MI
Re: IAC count ? As the Colonel has pointed out, the only two things IAC is really doing is smoothing out the idle while the engine warms up and keep the car from stalling when you jump on the breaks to stop at the red lights.
Heads and Cam cars drill out the TB hole to allow a bit more air flow at idle which smooths the idle warm up and results in a lower IAC because it no longer needs to have the PCM hunt using the IAC for increased air flow. As a result the IAC stablizes and you see less surging at startup and you won't stall when you jump on the breaks to stop. Been there, Stalled that. <img src="gr_grin.gif" border="0">
Over drilling the TB means the IAC may drop to 0 as the PCM sees the extra air coming in. So now the PCM has no way to reduce air flow as a method to smooth the idle or adjust to envirnonmental changes.
Is this really bad if your car sounds smooth at startup?
The only thing that sounds potentially bad is that if the car does have a fixed fuel demand based on the idle RPM then we are getting more air than what the PCM wants resulting in a leaner than desired target mix??? The extra air from 1/64" to 1/32" hole overbore is probably not a real problem at idle rpms.
Perhaps the biggest risk that comes to mind would be the potential that the pintel gets stuck from being closed most of the time, but if I'm smooth at idle and I'm not throwing any SES codes, what's the real harm.
Just some rambling thoughts to throw into the discussions. <img src="gr_grin.gif" border="0">
Rick
Heads and Cam cars drill out the TB hole to allow a bit more air flow at idle which smooths the idle warm up and results in a lower IAC because it no longer needs to have the PCM hunt using the IAC for increased air flow. As a result the IAC stablizes and you see less surging at startup and you won't stall when you jump on the breaks to stop. Been there, Stalled that. <img src="gr_grin.gif" border="0">
Over drilling the TB means the IAC may drop to 0 as the PCM sees the extra air coming in. So now the PCM has no way to reduce air flow as a method to smooth the idle or adjust to envirnonmental changes.
Is this really bad if your car sounds smooth at startup?
The only thing that sounds potentially bad is that if the car does have a fixed fuel demand based on the idle RPM then we are getting more air than what the PCM wants resulting in a leaner than desired target mix??? The extra air from 1/64" to 1/32" hole overbore is probably not a real problem at idle rpms.
Perhaps the biggest risk that comes to mind would be the potential that the pintel gets stuck from being closed most of the time, but if I'm smooth at idle and I'm not throwing any SES codes, what's the real harm.
Just some rambling thoughts to throw into the discussions. <img src="gr_grin.gif" border="0">
Rick
