Idle question about the 3.4DOHC with an automatic

[sspeedstreet]

Can someone describe to me the off-throttle to idle RPM drop of your car? Better description: If you're rolling along at say 20 mph, let off the throttle, put the trans in neutral and brake to a stop, what does the idle do? Does it immediately drop to a "parked idle" speed or does it hang at 1500 or so rpm til the speed drops to almost 0?

Odd question I know, but I'm thinking of having the 5-speed off-throttle programming redone to the automatic program on mine and I was wondering what that would give me.

Thanks,

Neil

[1988GTU]

If 5 speed, and A/C (accessory load applied) on, then I can see the reasoning for the idle to be in that range.

[robertisaar]

does it hang at 1500 or so rpm til the speed drops to almost 0?

this is what happens with MOST vehicles, not necessarily LQ1 specific. someone at GM, while wearing the Wizard Hat of Infinite Wisdom +50, decided that adding a set amount of IAC counts above x MPH(with an automatic) was necessary for whatever reason. you can see this to a smaller degree while in-gear, once you pass that MPH threshold, the idle speed correction code starts kicking in and spark and IAC counts start getting modified to reach the target speed. while above that threshold, they're running in an open loop fashion.

sometimes, switching between neutral and drive while at reasonable speeds can cause some odd things to happen as well. go from drive to neutral at 55MPH with no throttle and most of the time, the engine speed will jump. other times, it will drop down to a normal looking idle speed. i get the feeling that this is due to throttle follower settings and timing when you shift compared to when you let off the throttle is what determines which happens.