pcmhacking.net

Hi guys just wanted to share the issue I'm having at the moment trying to tune my motor for idle.
So basically the car is a vr ss running a heavily modified 355 , I'm using the 424 with an nvram and $11p with the lm2 analogue out wired into d8, all seems to be communicating well. I did have to modify the afr in the wideband 0-5v to get it to be the same as the lcd on the lm2 box.
So first up I'm trying to adjust my idle which isn't cooperating at the moment , the commanded idle is 950rpm and it's hovering around the 1100-1200 Mark.
In the data dash it shows the iac counts is at zero , It starts out at 60ish cold then comes down as its warmed up but hits zero and the idle obviously is too high . I've checked for vacuum leaks , closed the throttles completely as its running a aeriflow 1375cfm quad throttle body and it still doesn't help. I can put my finger partially over the iac intake hole on top of the throttle and the idle comes down, if I fully cover it the motor dies. Has anyone had trouble with the aeroflow units before ? I would have thought at 0 counts the air would be pretty much cut off to the iac feed hole.
Cheers guys

Possibly it's made to take an LS1 IAC solenoid and you have an older type fitted? If the throttle blades are closed and the idle track is flowing there's not a good seal. If you cover that track and the engine stalls then the butterflys are closed. From what I've read the LS1 solenoid has a bigger end. Possibly you are using an LS1 type already and it's something else.

I'm using the iac that came with the throttlebody , I'm almost certain it's something to do with the iac and not sealing properly . How does the pcm work out the iac is at 0 counts fully extended , or does it just go by so many steps within a range if you get what I mean ?
Just wondering if the pcm thinks it's at 0 but could still extend out further.

Has a similar problem 2 four barrel throttle bodies on 350 chev with a delco 808 ecu when the delco was commanding to close the iac was opening just using one iac stepper the stepper iac motor supplied with the throttle bodies was different to the holden one had to swap the four iac wires around to get it to work right the 2 coil wires didnt match up and then had to reverse one of the stepper coil wires