Hello

I want understand the IAC System in my 1989 Camaro Iroc-Z 305 TPI.
The Idle function is not hard to understand, but what happens when the car is moving ?

At Idle the IAC steps are at ~ 20. When you loosen the brake and let the car roll then the steps remain on 20. But if you accelerate the steps go to ~40 and stay there. In deceleration mode the steps are at ~ 50.

The problem is, i cannot find this values (40, 50) in the prom settings. ?
This values are a bit high, because in this case the idle is too high (~ 1500) and goes down to late (short before stop).

 

Describing all of the IAC functionality in $6E would be extensive. Here is a writeup on the $42 ('7747) IAC control:

https://www.thirdgen.org/techbb2/sho...hreadid=308613

Note the throttle follower (TF) logic, this is what is causing the IAC to open as you depress the go-pedal. The $42 IAC logic is much simpler then the $6E IAC logic, but the write up will help understand what is involved.

One thing to remember while reading it, is that it is different then the $6E logic. So don't expect to find them matching each other regarding parameters and the their use.

RBob.