Weird IAC Numbers - Idle Won't change

[Antbankstwo3]

So my car has actually been driving very good and still is. I recently got a new chip for my application a couple weeks from Turbo Tweak and has been running very strong since.

Randomly going thru my Scanmaster I noticed my IAC numbers are at "00" while in Park at idle. When I put it in gear and drive around the IAC numbers will increase like normal (unsure if they are where they should be tho).

I've tried to adjust it by turning the screw CCW until numbers start to register on the Scanmaster which I was able to do (4-8 was where it would start to register at). When I would try to get both IAC/TPS numbers where it needs to be, the IAC numbers wouldn't go higher than 8 or 9. I know it's "adjusting" tho though because the TPS number are changing and I would have to reset those as well. I reset the IAC and no luck.

One weird thing it's doing is, the idle will never change when I adjust the screw. Even when I backed it out to almost all the way, still no change in idle. I thought that was a bit strange as I was expecting it to start idling rough. I took the IAC valve out and cleaned it, still no changed. I ended up leaving IAC alone and the TPS numbers at .44 and called it a day.

I did take it for one last spin and it seems to be running fine. I never noticed issues with the numbers until I put the new chip TT chip in.

Any more ideas? Bad IAC valve maybe? When I first took it off the valve was not screwed in all the way. It was a bit loose. So not sure if that could affect anything with the valve over time. I have looked for vacuum leaks too and all looks well. One thing I did notice is the, PCV hose (rubber) going to the hard line (to vaccum block), that rubber hose is being sucked closed from the vacuum. Is it supposed to be that way? Is the PCV stuck?

Any help is greatly appreciated! Thank you everyone!

 

[whitehot1]

Are you setting it correctly ? Get the motor up to temp and Close the throttle blade till you see the IAC number raise . You are shooting for 15-20 at idle . Then readjust your TPS to .42-.46 . IAC numbers will raise when throttle blade is closed and reduce when you open the throttle Blade .

It could be that the IAC motor is defective.

 

[Antbankstwo3]

Are you setting it correctly ? Get the motor up to temp and Close the throttle blade till you see the IAC number raise . You are shooting for 15-20 at idle . Then readjust your TPS to .42-.46 . IAC numbers will raise when throttle blade is closed and reduce when you open the throttle Blade .

It could be that the IAC motor is defective.

Thanks for the reply! I have done this process several times on my own car and other TR's I've owned before this without any problems. Since it was acting weird this time, I thought I'd ask everyone here as I might be missing or skipping a step or someone might have add this same problem. I've even referenced back to the GNTTYPE web page for help and used the search portion here. I'm stuck at this point. I was thinking maybe defective IAC motor too. But wanted to elements all options before throwing parts at it.

 

[whitehot1]

There may be a way to test the IAC motor to see if it's getting weak from use or age, i don't know though.

The only way i know of is to swap it out with a known good one and see if it makes a difference.

The good thing about this electrical part is, it's not that expensive and the parts stores have them in stock. Some times buying a new part to see if it fixes a problem isn't a bad thing. At least you know if the one you replaced was good or bad,and if it was still good now you have a known good spare to add to your collection for troubleshooting in the future.

You can buy these IAC motors new off ebay dirt cheap, and they are major brands and free shipping.

I know my parts store would let me return the part for a refund if it didn't fix my problem. I'm not sure your parts store would do the same but you could try.

You could also try to see if there is someone close to you that would let you swap parts with. Post a thread here on the board in the Regional Forum section that you live in, never know could be someone right down the road.

What ever you decide to do, Good luck

 

[Chuck Leeper]

One thing I did notice is the, PCV hose (rubber) going to the hard line (to vaccum block), that rubber hose is being sucked closed from the vacuum. Is it supposed to be that way? Is the PCV stuck?

Fix this, B4 you do any other adjusting........

 

[haywire4130]

Are you running a larger than stock throttle body? Is your tv cable adjusted correctly (might not be allowing the throttle to close when the screw is backed out?)

 

[whitehot1]

If you conclude that the IAC valve is the problem. Here is one i just seen on ebay.

Idle Air Control valve
Condition: new
Brand: Standard Motors
Part Number: AC1
Ebay item number: 251629456683
Price: $8.99 shipped

 

[1986 Buick GX1]

Are you running a larger than stock throttle body? Is your tv cable adjusted correctly (might not be allowing the throttle to close when the screw is backed out?)

I've had the cruise control cable get tight and keep the throttle open while changing intake parts as well.

 

[Antbankstwo3]

Fix this, B4 you do any other adjusting........

Ok. Will do!

 

[Antbankstwo3]

There may be a way to test the IAC motor to see if it's getting weak from use or age, i don't know though.

The only way i know of is to swap it out with a known good one and see if it makes a difference.

The good thing about this electrical part is, it's not that expensive and the parts stores have them in stock. Some times buying a new part to see if it fixes a problem isn't a bad thing. At least you know if the one you replaced was good or bad,and if it was still good now you have a known good spare to add to your collection for troubleshooting in the future.

You can buy these IAC motors new off ebay dirt cheap, and they are major brands and free shipping.

I know my parts store would let me return the part for a refund if it didn't fix my problem. I'm not sure your parts store would do the same but you could try.

You could also try to see if there is someone close to you that would let you swap parts with. Post a thread here on the board in the Regional Forum section that you live in, never know could be someone right down the road.

What ever you decide to do, Good luck

I appreciate the insight and advice!

 

[Antbankstwo3]

Are you running a larger than stock throttle body? Is your tv cable adjusted correctly (might not be allowing the throttle to close when the screw is backed out?)

I'm running the stock one. I'm not sure about that cable. Never have had to adjust it. I can check it out tho. If it does need adjusting, how would I know and how would I adjust it?

Thanks for the advice.

 

[Antbankstwo3]

If you conclude that the IAC valve is the problem. Here is one i just seen on ebay.

Idle Air Control valve
Condition: new
Brand: Standard Motors
Part Number: AC1
Ebay item number: 251629456683
Price: $8.99 shipped

Oh awesome thank you for this!

 

[Antbankstwo3]

I've had the cruise control cable get tight and keep the throttle open while changing intake parts as well.

I never thought of that! I will give that a love as
well.

 

[Shawn N]

Hmmm that's a odd one. Car should start/die with 0 IAC or at least idle poorly but should increase rpm's if the throttle blade screw is backed out. Have you taken the throttle body off and inspected the airway for the IAC? Maybe blocked by debris and or oil build up. The gm part number is 25527077 for IAC.

 

[Antbankstwo3]

Hmmm that's a odd one. Car should start/die with 0 IAC or at least idle poorly but should increase rpm's if the throttle blade screw is backed out. Have you taken the throttle body off and inspected the airway for the tps? Maybe blocked by debris and or oil build up. The gm part number is 25527077 for IAC.

Thank u did the info!