Because of this thread, I've been monitoring my idle closely. A few observations and some backgroud regarding my settings:

My target idle at warm coolant temps is set to 800 rpm.

My warm IAC park position table is set to 20 counts for the same warm coolant temps.

At 20 counts, my car will idle at about 850 rpm. It will remain slightly above the target rpm. It seems that if the rpm does not fall below the target rpm, the IAC position can be held up by the warm IAC park position table settings.

It appears that if the idle is consistently above the target rpm, it may stay there depending upon the settings in the table.

There is a min underspeed error condition for entering the PID control. It seems that the actual rpm must drop below the target by the minimum underspeed error in order to be "controlled".

After lowering the warm IAC park position table down to 15 counts, the idle now will drop below the target value of 800 rpm and then be controlled to 800 rpm with approximately 18 counts +/-1 in today's air.

With the previous settings, it would stay at 20 counts and idle slightly above the target.

Due to this behavior, it would appear that the warm IAC park position table should be calibrated slightly below the actual airflow needs.

From what has been described, I don't think this effect is causing the problems with mk842766's car since it has already been stated that the warm IAC park position table was set to only 5 counts and it has also been reported that the IAC position is closing to zero.

Just passing along some information that may be usefull.

 

I'm learning alot here.

 

God help me, I hope it doesn't come to that!! I've already had to track down, and replace more of this 25 year old wiring than I ever wanted to do...I'll start looking at those connections, and give the one within easy reach a close inspection....but it's been my experience that the bad spots are NEVER the one's within easy reach....Thanks for the input!

Cheers,
Michael

 

More idle info:

I've located the parameter that adds the offset to the Warm IAC park position vs coolant temp table when the vehicle is in motion.

For manual transmissions this value is typically set to 10 counts and 5 counts for autos.

For $32B masks: this parameter address is 689.
For $32 masks: this parameter address is 683.
For $6E masks: this parameter address is 57A.

Note: The preceding byte in each of the masks is a switch for manual/auto. (1 = manual). Autos apparently also check for drive.

I've noticed the presence of the offset while scanning and rolling in gear, but I hadn't found the address in the $32B mask until now.

Up to now, I've been tuning the Warm IAC park position table for this purpose, to control the speed and rpm for rolling in gear, but this can cause a comprimise between an acceptable minimum value to still permit normal PID idle control when stopped and still maintain sufficient air for rolling in gear.

Adjusting the offset and table allows for independent tuning of both of these effects.

I've recently lowered the park position down to 15 counts to prevent it from holding my idle up. However, when rolling in gear with this change, the 15 counts + the 10 count offset = 25 counts is still too low to lug uphill at idle in 2nd gear.

Now raising the offset to 15-20 counts will correct this and improve the lugging performance in gear, without negatively impacting the PID idle control.

That is all for now.

Update: I tested it tonight, and it works as expected. I set the warm IAC park position to 16 counts and the offset to 19 counts. When rolling in a warm idle in gear, I'm seeing the correct number of counts (16+19) = 35. In today's 95 degree air, it was a little sluggish idling uphill in 2nd gear. Looks like I need to add a few more counts to the offset to get it where I want it.

Also, when in PID control the car was idling at 800 rpm between 16 and 19 counts, so its not being held up by the park position.