Unusual IAC issue

brian

Senior Member
Joined
Jul 4, 2001
Well, Here goes...

I got an all around running 87 T in August. But, the idle has been a little weird. IAC counts are from 55-65 in park, 60-70 in gear hot. So, I do the IAC reset procedure, it comes down to between 0-20 in gear.... WOW! I got it! Not so fast... It was good until, I shut the car off. Now, it went back up to 60-70 in gear. Which is not "all that" bad. But, the car still has a surge to it at idle I would like to resolve. (at least minimize)

The procedure I have done is the "IAC Reset Procedure" from GNTTYPE, and is from the service manual. When it gets scary is when I start the car with the IAC unplugged. It runs at 2300 with the throttle screw not touching the throttle arm. It will slowly return to 800-900 upon being plgged back in.

So, now the car still has a weird idle at times, and during a warm start will rev to 2000 rpm, before slowly droping down to "normal" rpm.

The BLM`s are at 122 hot and idling. So, it should not have any vacuum leaks. It had an new IAC put in yesterday.
I am stumped and confused. Any help would be appreciated.

Brian
 
Well, Here goes...

I got an all around running 87 T in August. But, the idle has been a little weird. IAC counts are from 55-65 in park, 60-70 in gear hot. So, I do the IAC reset procedure, it comes down to between 0-20 in gear.... WOW! I got it! Not so fast... It was good until, I shut the car off. Now, it went back up to 60-70 in gear. Which is not "all that" bad. But, the car still has a surge to it at idle I would like to resolve. (at least minimize)


Brian

did u set the IAC in gear like u said or did u mean in park because ur suppose to set it 10-30counts in park car warm and it will probably be around 50 in gear. my car has always had some sort of surge at idle, car is idling normal and then all the sudden the idle bumps up a hair and tries to overpower my brake pedal. does it more with A/C on. never could figure it out, just came to the conclusion that the car is slightly retarded!

oh what kind of chip does it have?
 
I am using an old Commander chip.

I am just trying to get the car to be in the specified range "either" way.:smile:
Gotta get it, one or the other. I would accept it if it was good at either.:D

Brian
 
Did you check the tps and reset it if needed, after adjusting the air screw? You need to keep the key off for 5-7 seconds minimum after adjusting either, before restarting, to give the ecm time to fully park the iac. Pull the uppipe off, remove the iac, and hose out everything with carb cleaner in case the passage is full of goo. Could also have a vacuum leak so look at all those old hoses :). I like 10-20 iac counts idling in gear fully warmed up, and let the p/n counts go where they will.
 
Well, Here goes...

I got an all around running 87 T in August. But, the idle has been a little weird. IAC counts are from 55-65 in park, 60-70 in gear hot. So, I do the IAC reset procedure, it comes down to between 0-20 in gear.... WOW! I got it! Not so fast... It was good until, I shut the car off. Now, it went back up to 60-70 in gear. Which is not "all that" bad. But, the car still has a surge to it at idle I would like to resolve. (at least minimize)

The procedure I have done is the "IAC Reset Procedure" from GNTTYPE, and is from the service manual. When it gets scary is when I start the car with the IAC unplugged. It runs at 2300 with the throttle screw not touching the throttle arm. It will slowly return to 800-900 upon being plgged back in.

So, now the car still has a weird idle at times, and during a warm start will rev to 2000 rpm, before slowly droping down to "normal" rpm.

The BLM`s are at 122 hot and idling. So, it should not have any vacuum leaks. It had an new IAC put in yesterday.
I am stumped and confused. Any help would be appreciated.

Brian

Did you do the "reset procedure" (which sucks BTW), or did you actually adjust the minimum air bleed screw to obtain the correct IAC values.
You can either use the "reset" procedure, or I can give you a little right up here on how to do it correctly.
 
Did you do the "reset procedure" (which sucks BTW), or did you actually adjust the minimum air bleed screw to obtain the correct IAC values.
You can either use the "reset" procedure, or I can give you a little right up here on how to do it correctly.


I did use the reset procedure.
My bleed screw does not even touch. If it does, it idles about 1200 rpm. When I unplug the IAC the engine races to 2300 instead of 500-550 like it is supposed to.
Exactly how far in is the screw supposed to be in, with the factory adjustment? If I turn the screw in to touch the bracket, will lowering the TPS from lets say .52, back to .44 or so bring the idle down?
No matter what I have done, except for the first time I adjusted it... I can not get the counts under 50 minimum. This is HOT at idle in park.

Could bad seals in the throttle body cause this? As the air is coming in after the maf. I am not sure if mine are leaking. Just a thought.:redface:

Brian
 
Did you check the tps and reset it if needed, after adjusting the air screw? You need to keep the key off for 5-7 seconds minimum after adjusting either, before restarting, to give the ecm time to fully park the iac. Pull the uppipe off, remove the iac, and hose out everything with carb cleaner in case the passage is full of goo. Could also have a vacuum leak so look at all those old hoses :). I like 10-20 iac counts idling in gear fully warmed up, and let the p/n counts go where they will.


I had to reread your post after writing mine. I see that I am starting to get where you are going here. I may not be waiting long enough. Plus...
It seems as when I did this years ago on another car, it had to be done in smaller steps then I was taking.:eek: My adjustments where to far large, and I had to go back and slow dddooowwwwnnnn.:wink:

Brian
 
I had to reread your post after writing mine. I see that I am starting to get where you are going here. I may not be waiting long enough. Plus...
It seems as when I did this years ago on another car, it had to be done in smaller steps then I was taking.:eek: My adjustments where to far large, and I had to go back and slow dddooowwwwnnnn.:wink:

Brian

Yes, the air bleed (minimum air bleed screw) needs to be done in smaller steps. But the screw will be close if you can see one thread on the opposite side (nearest touch point) from the srew head.
Turning the screw CW will temporarilly increase rpms, causing the IAC numbers to decrease to compensate, and bring the idle back down. Do it one turn at a time, and re-adjust the TPS idle value to keep it in spec. back and forth until you get your IAC numbers (in park/neutral) to be around 10-20. This will yield numbers about 10 or so higher when in gear.

Conversely, turning the screw CCW will cause an increase in numbers (for those folks that have numbers too low).

90% of the time the "reset" procedure will do NOTHING but get folks in trouble and "all wrapped around the axle" thinking it's going to cure bad IAC numbers, when in actuallity it won't.
 
90% of the time the "reset" procedure will do NOTHING but get folks in trouble and "all wrapped around the axle" thinking it's going to cure bad IAC numbers, when in actuallity it won't.[/QUOTE]

Thanks for the tips. My thinking was off, but you and Carl have brought me back from the brink of insanity!:p
Just need to start over, and go smaller steps.

I will report on my findings!:wink:

THANK YOU!

Brian
 
Kind of add on Q here

When I pulled my old one out it was over the 1 1/8th anyway the spring was bent and you could see it bottomed out and jammed.

Now when I pulled new one out of the box it was same lenght so with two different methods in front of me 1. push on pintle to retract (didnt seem to work) and the other which was I pulled spring back and turned the pintle to get it under the 1 1/8 (reset spring in notch)

Now is it posible that I might have turned it in to far causing it to not seat? or is there more adjustment inside? that would allow it to extend until seated?
So in other words the initial adjustment was ment for install only so it would not bind up when I tightened down on it?

Im only talking about maybe 2mm below 1 1/8 but if I get my numbers to where most folks say and my screw is just poking through..maybe 1 and half threads my idle is real shaky. but im also battle'n a bad injector so I'll stick with my question above and that was IAC pintle adjustment.

mike
 
:biggrin: Thanks for the tips!:biggrin:

Got `er all set up this afternoon. I now have "about" 1 thread showing, as instructed.
The biggest thing that helped was small adjustments. This did the trick and Big Blue is idling like a new car!

Thanks again for the support!

Brian
 
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