An Idle Discussion..

[gbmidyear66]

I am still not happy with the way my car idles - although it now appears to be functioning 100% as GM intended it to as shipped from the factory.

I have the original GM AUAH PROM. With this PROM, my car will idle down to 700, which I am reasonably happy with. What I don't like about the AUAH (besides the 1-4 shift and hot run temp) is that if the car is in motion the car will idle at about 1500 PRM, after you come to a stop it will drop down to baseline idle of about 700RPM after about 4 seconds (the ECM idle request speed is 650). I endure a fair bit of stop and go and find this behaviour pretty annoying.

I also have a DRM PROM. With this PROM the car will idle at about 1200 RPM when in motion, then about 2 seconds after coming to a full stop, will drop down to about 800RPM baseline idle (ECM requested idle is 750).

I would really like to get rid of the high idle when in motion, and have it drop down to baseline if in neutral or stopped within a second or so.

I spoke to Marc Haibeck today. He indicated the AUAH behaviour is as designed at that time, and that the AYBK will drop down to baseline faster, after about 2 seconds. His current PROM is based on AYBK and has same idle behaviour as AYBK He indicated he has had a few people raise the same issue as me and that he is planning to look at this as a winter project later this year. He indicated that the 93 and later cars will run at abou 1,000 RPM when in motion, then dop down to baseline quicker after coming to a full stop. He hopes to decipher the code and make this mode available for earlier cars.

Maybe I am just too picky, but am really hoping Marc can cracik the code and offer an improved idle behaviour for my 90.

[tpepmeie]

This is most definitely adjustable in the calibration. There are a couple of different variables at play, but it can be set to drop to idle speed while in motion. It is mph driven. Marc will crack it, I'm sure.

[XfireZ51]

Originally Posted by tpepmeie

This is most definitely adjustable in the calibration. There are a couple of different variables at play, but it can be set to drop to idle speed while in motion. It is mph driven. Marc will crack it, I'm sure.

I changed mine to run at that way.

[gbmidyear66]

Domenic, do telll...

Who did your tuning/PROM? Marc doers not offer this feature yet.

Glenn

[XfireZ51]

Originally Posted by gbmidyear66

Domenic, do telll...

Who did your tuning/PROM? Marc doers not offer this feature yet.

Glenn

I do. As Todd has hinted, it's part of the IAC settings. There's a table for # of IAC steps v MPH. The elevated idle with vehicle moving is used for Decel and is part of emissions. The rate of IAC decay is also managed by the calibration ie quick v slower IAC drop.