IAC valve Pintle adjustment

'88 Suburban 350 TBI/TH700, 4x4
The subject line says it, what is the proper adjustment for the pintle?

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"Shades" wrote

What are you asking? There is no "manual" adjustment for an IAC (at least, none that I'm aware of). Are you asking what it's position should on a normally operating system? If so, I believe that you would be looking for around the 20-30 count range.
The IAC valve simply tries to follow orders from the PCM. The PCM requests a certain RPM, the IAC opens and closes the pintle in response to the request. It will try to maintain whatever the PCM is asking, in regards to the idle speed.
Ian
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On Mon, 17 May 2004 01:39:19 GMT, "shiden_Kai"

Interesting. This has an IAC?
I asked becuase I just picked up a similar vehicle, an 88 Suburban 350 TBI 700r4 4x4. It idles a bit high so I thought I needed to adjust something. If the ECM is doing it then there's not much for me to do.
Lot's of other things on the punch list before I get to the idle.
-RC
R.Clarke spam snipped-for-privacy@BlocKmindspring.com RTP, NC, USA
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On Mon, 17 May 2004 01:57:09 GMT, R Clarke

and start spraying vacuum hoses and the TBI base gasket and listen for the idle to change. if it does change, the part you've just sprayed is leaking.
hth, Bret
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I can turn the pintle on the IAC valve and it will screw in or out depending on which way I turn it... Pintle adjustment was mentioned before and so I was wondering.
| '88 Suburban 350 TBI/TH700, 4x4 | | The subject line says it, what is the proper adjustment for the pintle? | |
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the TBI unit. On these, I think that the only adjustment is to hold the unit in your hands and push the pintle with your thumb (you may have to wiggle the pintle to get it to move). Then you re-install the IAC and drive the vehicle, it will re-set itself automatically (I tink that 40 mph is the magic number for reset). This is how it works on my '90 and on an '85 that I used to have so I'm guessing it's the same. Rich B
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% There are two classes of pedestrians in these days of reckless motor traffic - the quick and the dead. ~ Lord Dewar 1933 ~
Climbing into a hot car is like buckling on a pistol. It is the great equalizer. ~ Henry G. Felsen 1964 ~
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What GM in '85 had TBI? What do I set the 'base' distance at? It screws in and out manually???
(Shades) | >'88 Suburban 350 TBI/TH700, 4x4 | >The subject line says it, what is the proper | >adjustment for the pintle? | > | If you have the TBI 220 (dual injector TBI) the IAC should screw into | the TBI unit. On these, I think that the only adjustment is to hold the | unit in your hands and push the pintle with your thumb (you may have to | wiggle the pintle to get it to move). Then you re-install the IAC and | drive the vehicle, it will re-set itself automatically (I tink that 40 | mph is the magic number for reset). This is how it works on my '90 and | on an '85 that I used to have so I'm guessing it's the same. Rich B | | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | There are two classes of pedestrians in these days of reckless motor | traffic - the quick and the dead. | ~ Lord Dewar 1933 ~ | | Climbing into a hot car is like buckling on a pistol. It is the great | equalizer. ~ Henry G. Felsen 1964 ~ |
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It was a 1985 Celebrity with the 2.5L 4 cylinder. I know that it's not the 5.7 but the IAC valves are almost interchaneable. There is a minimum clearance on the pintle but I don't know what that is. The only IAC that I found where they mention a setting is the flange mount style that is used on the larger engines (larger than a 350). The only things mentioned, for the screw-in mount IAC valve, in any manuals that I have is to push the pintle in so that it doesn't hit the seat when you install it. I have never tried to screw the pintle back into the valve.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% There are two classes of pedestrians in these days of reckless motor traffic - the quick and the dead. ~ Lord Dewar 1933 ~
Climbing into a hot car is like buckling on a pistol. It is the great equalizer. ~ Henry G. Felsen 1964 ~
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Maybe he's talking about the base idle screw procedure?
There is a procedure for that, which involves removing the IAC, and setting the base idle screw.
If that is what he means, I can explain that, but I think that went out with OBD1 if I'm not mistaken.
However, it is an 85.
Refinish King

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To set the base idle, the procedure is at the end of the service manual section for the TBI. There's a t20 or t25 throttle speed adjusment screw on the TBI...the IAC is not adjustable, except by the ECM. In drive, at 550rpm , use should see around 12-14 counts on your scanner for the IAC. Doug
Refinish King wrote:

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Keep in mind, prior to making that adjustment you must confirm that there are no vacuum leaks or other problems that would cause idle problems. If you must make that adjust you will have to reset the ECM by pulling the fuses after each adjustment. This is also a great way to get a sticking butterfly free.
Rita
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OK! LAST time! The new IAC valve that I bought DOES have an adjustable pintle!!! Turn it right and it will shorten, turn it left to lengthen!!!
EVERYWHERE I have read says that the Idle RPM is ECM controlled. Where the idle screw is located is capped off and I am not gonna pop the cap to monkey with it cuz the butterflies are completely closed.
WHAT should be about 12-14 counts on what scanner????
| > | >>It was a 1985 Celebrity with the 2.5L 4 cylinder. I know that it's not | >>the 5.7 but the IAC valves are almost interchaneable. There is a | >>minimum clearance on the pintle but I don't know what that is. The only | >>IAC that I found where they mention a setting is the flange mount style | >>that is used on the larger engines (larger than a 350). The only things | >>mentioned, for the screw-in mount IAC valve, in any manuals that I have | >>is to push the pintle in so that it doesn't hit the seat when you | >>install it. I have never tried to screw the pintle back into the valve. | >> | >>%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | >>There are two classes of pedestrians in these days of reckless motor | >>traffic - the quick and the dead. | >>~ Lord Dewar 1933 ~ | >> | >>Climbing into a hot car is like buckling on a pistol. It is the great | >>equalizer. ~ Henry G. Felsen 1964 ~ | >> | > | > | > | > |
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wrote:

Dude, there is no spec. you just need to keep it from hitting the seat when it's first installed. so screw it all the way in. the 12-14 counts would be on any scanner you connect to the ALDL that can read the ECM data stream (I use a Snap-On MT2500). BTW, the idle screw is an controlled air leak around the butterflies, they're supposed to be closed. all that screw does is set the baseline so the IAC can be set in the middle of it's range for a normal idle.
HTH, Bret
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"Shades" wrote

Well, I guess you are the expert. Don't bother listening to others who tell you that there is no adjustment on the IAC. All you are doing when you turn it one way or the other is simply doing what the ECM is going to do when it decides where the pintle is going to be. Don't you understand how an IAC motor works? It has a small motor that (wonder of wonders) turns and in the process screws the pintle in and out. You are just doing the reverse procedure and thinking that you have found some sort of adjustment.
It's quite possible that you might have to do some type of IAC idle relearn procedure, but there is no manual adjustment that you do to the IAC.

So you believe that, but you don't believe that there is no adjustment on the IAC? The screw you are looking at is "minimum idle" and really has very little bearing on what the IAC does.

The IAC is a stepper motor and it moves the pintle in and out so many counts depending on where the idle is supposed to be. The "counts" are an indication of where the IAC is locating the pintle at idle.
Ian
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So how far from the seat does it need to be? .005??? .500???
| It was a 1985 Celebrity with the 2.5L 4 cylinder. I know that it's not | the 5.7 but the IAC valves are almost interchaneable. There is a | minimum clearance on the pintle but I don't know what that is. The only | IAC that I found where they mention a setting is the flange mount style | that is used on the larger engines (larger than a 350). The only things | mentioned, for the screw-in mount IAC valve, in any manuals that I have | is to push the pintle in so that it doesn't hit the seat when you | install it. I have never tried to screw the pintle back into the valve. | | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | There are two classes of pedestrians in these days of reckless motor | traffic - the quick and the dead. | ~ Lord Dewar 1933 ~ | | Climbing into a hot car is like buckling on a pistol. It is the great | equalizer. ~ Henry G. Felsen 1964 ~ |
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Far enough back so that:
It doesn't hit the seat at any time, while you're screwing it in and tightening it.
Refinish king

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You don't!
You are actually supposed to energize it, and retract it to the extreme open position. Meaning the valve is in the motor housing, then start the car, it will go to open loop position till the fan comes on.
This is the first I've heard of the 40 MPH, unless you're working on a F.O.R.D., which then you would keep the car at a constant 15 to 20 MPH for 5 to 10 minutes, or you hit something. Whichever comes first, then the volatile memory in the computer was set.
Refinish King
(Shades)

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(Shades) | > | >'88 Suburban 350 TBI/TH700, 4x4 | > | >The subject line says it, what is the proper | > | >adjustment for the pintle? | > | > | > | If you have the TBI 220 (dual injector TBI) the IAC should screw into | > | the TBI unit. On these, I think that the only adjustment is to hold the | > | unit in your hands and push the pintle with your thumb (you may have to | > | wiggle the pintle to get it to move). Then you re-install the IAC and | > | drive the vehicle, it will re-set itself automatically (I tink that 40 | > | mph is the magic number for reset). This is how it works on my '90 and | > | on an '85 that I used to have so I'm guessing it's the same. Rich B | > | | > | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% | > | There are two classes of pedestrians in these days of reckless motor | > | traffic - the quick and the dead. | > | ~ Lord Dewar 1933 ~ | > | | > | Climbing into a hot car is like buckling on a pistol. It is the great | > | equalizer. ~ Henry G. Felsen 1964 ~ | > | | > | > | | |
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You energize it and put it in as far as it will go before installing it,
That's what I was getting at, and your vehicle doesn't have an electrical cooling fan, another mistake on my part. So you would have to wait till it goes into closed loop on the scan tool.
Don't mess with the IAC too much, otherwise you'll have a $50.00 pile of shit in your hands!
Refinish King
(Shades)

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