Understanding IAC while idle tuning

[nonnieselman]

I've read all of the writeups on idle tuning that I can find.

I'm trying to understand IAC steps.
I see alot of guys saying they are seeing 80-100 steps at idle with a larger cam.

I have a 212/212 .561/.561 114+3 cam in a LM7 5.3 and 80# FIC injectors and BW S475/83 turbo running COS5 / 2 BAR Map.
Really really simple setup.
My problem is I'm seeing higher Steps.
750 rpm idle
Throttle stop set high as possible for a 0% TPS reading.
I've got the idle tuned pretty good so it starts up and runs great cold and hot. AFR is high 14s. Timing is around 20* average.

Why am I seeing 185-220 steps?

[LastCall]

I've read all of the writeups on idle tuning that I can find.

I'm trying to understand IAC steps.
I see alot of guys saying they are seeing 80-100 steps at idle with a larger cam.

I have a 212/212 .561/.561 114+3 cam in a LM7 5.3 and 80# FIC injectors and BW S475/83 turbo running COS5 / 2 BAR Map.
Really really simple setup.
My problem is I'm seeing higher Steps.
750 rpm idle
Throttle stop set high as possible for a 0% TPS reading.
I've got the idle tuned pretty good so it starts up and runs great cold and hot. AFR is high 14s. Timing is around 20* average.

Why am I seeing 185-220 steps?

The steps are how much the IAC is opening to allow more airflow through the IAC passage to achieve idle RPM. Opening blade or drilling throttle blade will reduce the steps required to maintain idle rpm and give the IAC more range.

[nonnieselman]

I understand that much.
Higher Steps means more air flow.
But with my throttle stop adjusted as far as it will go and still relearn at 0.0% my IAC steps seem a good bit higher than most folks with larger cam.

Just was going to see if i could figure out why it was. It idles great so its no concern.

[LastCall]

I understand that much.
Higher Steps means more air flow.
But with my throttle stop adjusted as far as it will go and still relearn at 0.0% my IAC steps seem a good bit higher than most folks with larger cam.

Just was going to see if i could figure out why it was. It idles great so its no concern.

Stock TB?

But if idle is good, including cold start, then I don't see a need to do anything. I have been able to open them quite a bit with the factory set screw and still get them reset and counts down.

[nonnieselman]

Yep. Stock 2002 5.3 Cable TB with new GM IAC and TPS.
Idle is good. Was just wondering how these guys were getting low Steps with a much larger cam is all.
Ill tinker with it later and see what happens.

[LastCall]

Yep. Stock 2002 5.3 Cable TB with new GM IAC and TPS.
Idle is good. Was just wondering how these guys were getting low Steps with a much larger cam is all.
Ill tinker with it later and see what happens.

Are you resetting the TPS as you crack the blade open? I have had some really big cams operate at 50 steps hot P/N and idle around 800-850 rpm.

Process I usually follow is to get engine to hot operating temp in park, crack blade via the screw until steps go to 60-80 (small cam). Turn engine off, disconnect TPS, turn ignition on for 10-15 seconds, turn off, plug in. and then restart. Should be reset to 0%.

[nonnieselman]

Yea, i reset it and check it to make sure its 0.0%.
If i go any further that where it is at now, it goes to 0.4 - 1% and wont reset to 0. So i backed it down till i seen 0%.

[LastCall]

Yea, i reset it and check it to make sure its 0.0%.
If i go any further that where it is at now, it goes to 0.4 - 1% and wont reset to 0. So i backed it down till i seen 0%.

If you need to, you can open up the idle percentage to 1% in the tube and if you are at .4% or .8% it will still enter idle mode. But it sounds like idle quality is fine as is. On some cars where this is an issue, you have to open the hole on the TB.

[nonnieselman]

I really thought about measuring the hole in the TB and enlarging it to the next size bit i have. I do have a spare TB so im not worried about going too far. Ill also clean the IAC just for the heck of it.

[statesman]

Is this a stock throttle body or an aftermarket?

[nonnieselman]

Factory Truck Cable TB.
My buddy bought it new from GM when he had it in his truck.
Ive never paid much attn to IAC so its probably nothing wrong just what it is.
But today going to lunch i made a log and noticed when i got back in the parking lot and put it in neutral it settled down to the 120s then i killed it.
I lowered my RPMs from 750 to 650 so ill see how it reacts. Then ill take it off and see if its dirty.