Target idle.

[jameslleary]

Can somebody open up ASDU and see what the Idle is set at? I have done the proceedure a few times for minimum air, but its still not right. I just want to make sure that I am going for the right idle speed. I have seen some posts on the net saying 525 +/-25 in drive, but I cant get it down to the 425 range. I must have the wrong info.
PS-Still have not found an OBD1 tuning App for iPad...I would do it myself if I could.

[gregs78cam]

I think the target idle - 100rpm is only an estimate, just to make sure that the IAC has a little bit of range below target idle. If you can get the idle you want with between 10 and 20 IAC counts you should be fine.

[jameslleary]

Thanks...I have no way to log, all i have is a hand held tach. I know that it needs to be set 100 below target, I just need to know what target is. This is a Factory ASDU prom....not modded.

[EagleMark]

ASDU is 525 stock totally warmed up in closed loop. If you can't get it that low just get it lower then that and stable.

Without looking at data it's a little harder. Drive around and get warmed up, turn off and cross A and B of ALDL plug, turn key on, unplug IAC, start engine and rev to 1500ish RPM for a minute to insure CL timer delay is met and O2 is warm and gone closed loop. Then set idle below 525.

[jameslleary]

Is that the minimum idle air setting, or the actual idle speed in drive(Target)?
Edit: never mind....i got it, thanks Mark!

[Scorp1us]

What is OL timer delay?

[EagleMark]

What is OL timer delay?

I made a mistake in that post above and will change it to CL where it says OL. (Closed Loop / Open Loop)

There's several OL and CL delays depending on the bin file. Some bins are OL idle and some are CL idle. So depending on the bin there is a delay going from CL while driving to OL idle. There is always a CL delay when started on these to insure O2 is warm enough.

[black dawg]

Does it have to stay in closed loop to set this min spec? I have never heard of setting the idle 100rpm lower than spec, is this actually needed?

[Scorp1us]

Hrm, yes, getting a vehicle into OL while warm and at a stop would be hard.

BD: yes, it shouldn't be in Open loop at all. in open loop it's not looking at the O2 sensor. But the reason why you set it to 100 less is that the IAC should be closed when you do this. Later when the IAC is partially open, it will be putting more gas in for the air coming from the IAC and will increase the idle speed. Then if you're worried about drive or AC being on, there are "bumps" to the idle for those.

[EagleMark]

Yes it has to be in closed loop for this procedure to work properly because the taget idle speed is set from the "IAC - Desired C/L Idle Speed" table.

It's not an idle setting, it's a minimum air setting. Your trying to get as much air past throttle blades as possible but still let IAC control idle.

Is it needed? Usually no. If your TBI system is stock with less then 125K miles it is probably fine, if you find your throttle sticking and jerks open when you hit the gas, but does not jerk open with engine off, then yes it's needed as the throttle shaft has worn and blades are not open enough. If a conversion to another engine it is usually needed. If your warmed up Closed Loop idle IAC counts are more then about 50 - 60 it is needed.

[black dawg]

OK, it must be lack of closed loop that is giving me problems. I just converted my 91 burb from 350 to 454, and have the 454 throttle body and prom. It goes into CL easy enough when you fast idle it, but falls out almost immediatly when it idles. Probably because of the open manifolds? Hopefully will get the exhaust finished up by the weekend.

[EagleMark]

Could be the open manifolds or BB could very well be an Open Loop idle.

Start a thread for your project and post up the bin and we will try and help.

[jameslleary]

Ok, I have set the min air at 525ish...in that neighborhood anyway. Idle is surging pretty bad. She idles a little high, wont kick down below 800 until put in gear.
When the idle finally gets drops to around 550-600, it surges.
No vac leaks.
Fuel pressure at 13 psi.
No codes.
Brand new Walker stock replacement exhaust, with new Manifolds.
TPS checks out good on the DVOM.
There is a sucking noise, that sounds like its coming from the steering box when it surges. Going to unhook all vacuum operated accessories to see if it clears up.

[jameslleary]

I think my tach might be BSIng me. Seems like 550(per this tach)is too low.

[EagleMark]

Without a scanner or TunerPro software and a cable it's hard to get anything right and know what's going on...