Ronny

iTrader: (1)

what is it and what function does it serve? when does one change the values in it as far as improving state of tune? i see it refered to once and awhile(OAAW) in various posts. i do not see it in TC but i assume i could request it to be added.

3.8TransAM

Throttle follower is basically the way the IAC works in relation to throttle opening/closing.. They basically chase the TB from the factory with the IAC and antistall strategies etc...

Do a search, quite a few good posts on it....

Not sure if directly your ecm or not, but still relevant nonetheless

later
Jeremy

Grumpy

The T/F function is to prevent rich spikes on sudden throttle closures. An intake always has a certain amount of fuel just laying around, and when the thottle snaps closed the intake vac level goes extremely high, causing any fuel to evaporate. That would lead to a real rich spike for just an instant. So with the IAC opened slightly there is some air bleed in, so that the spike of richness, isn't as bad.

Ronny

iTrader: (1)

so if i am cruising at say 50 mph and release the throttle abruptly i should see my IAC counts go from zero to a larger #? makes sense to me. i will verify. learn more every day. thanks.

RednGold86Z

iTrader: (1)

Throttle follower also functions to get the IAC open for a smooth controlled return to idle, and if it follows the throttle, it shouldn't be noticed by the driver. If say it were only RPM follower, the car could drive itself (bad). If it were to be an inverse throttle follower (open only when the throttle closes) it could possibly create a jerky condition when released. If the IAC were to stay still, and wait for the throttle to be released on the return to idle, it would be low enough already, and the PID would either have to predict that it doesn't need to move when it approaches idle, or it'll close some, and then open some to get the idle speed correct, which is just asking for trouble.

RednGold86Z

iTrader: (1)

It's also a shift improver for manual transmissions, and a decel reducer for autos. The "gulpe valve" feature is also a biggie as Grumpy stated.

JPrevost

It shouldn't go form 0 to a higher number, it still slows the engine down but the throttle follower does exactly what it's name suggests. It follows the throttle. So if you're cruising at 50mph and are still on the gas you'll see TF steps then when you lift the TF steps will SLOWLY decrease to slow down the engine's deceleration. It basically is not letting you close the throttle completely for emissions purposes. I hate the feeling of having a lot of TF so I limited it to 36 on my car to help get the engine speed down and then come slowely down to idle. Another reasons I don't like TF so much is it's power against my brakes. If the engine doesn't slow down fast and I need to get on the brakes I have to put extra effort into the brakes to stop the car.... crappy thirdgen brakes are to blaim but non the less it's a royal pain.

Ronny

iTrader: (1)

more clear. thanks again. i guess the IAC does more than i realized.

Grumpy

No, if you at a warm idle with a IAC count of say 14, and you acclerate, you'll see them jump to say 26, if you have a T/F value of 12. While cruising it'll stay around 26, and then as you come to a stop again you'll see them dip down. So in effect you have a min *high* idle, or an increased throttle opening all the time when moving and above idle.

Ronny

iTrader: (1)

thanks i will watch my IAC counts next log. is there ever a point where IAC count is zero and stays zero for a period of time? i think my warm CL idle IAC count is zero. almost positive. i have "commanded" idle speed at 700 but seldom see it. usually 800-900 range with no A/C on. would that suggest some air leaking in? i cant get idle any lower. sorry if off topic.