Question about IAC (Page 1/2)
A_Lonely_Potato SEP 02, 02:18 PM
Hey, I just got an 86 GT, and as to be expected on a 35 year old car, there's a list of things i have to fix lol. Its been idling pretty high(2.2k cold, 1.4k warm) and its making a terrible hissing noise. When I took of my IAC i noticed the port for it has a little rubber plug/cap over it. Searching through other threads and doing other googling, I cannot find anything about if this is supposed to be on there. Running the car without the cap didn't make a difference on the idle, and i suspect the IAC may be shot. It was pretty gunked up when I pulled it out, I cleaned it but that made no difference either. I'm going to pull it out and see if its moving at all in a bit, but figured I should find out for sure if this cap should be on there or not first. So for those who know, should I put it back on?

[This message has been edited by A_Lonely_Potato (edited 09-02-2021).]

Gall757 SEP 02, 05:07 PM
Welcome to the Forum!
Can you post a picture of the cap?

[This message has been edited by Gall757 (edited 09-02-2021).]

Patrick SEP 02, 05:16 PM

quote
Originally posted by A_Lonely_Potato:

When I took of my IAC i noticed the port for it has a little rubber plug/cap over it... figured I should find out for sure if this cap should be on there or not first.



Spud, post a photo of the "cap" in place.

[EDIT] If that vertical orange thing in your photo is the "cap" you're referring to, it has nothing to do with the IAC valve.

[This message has been edited by Patrick (edited 09-02-2021).]

fierofool SEP 02, 07:44 PM
That port with the orange cap should have a hard plastic line attached to it that runs over to the EGR solenoid. It should never be left open as it allows extra air into the combustion system. It can cause a high idle.

If you're messing with the IAC, the adjustment height of the pintle should not be more than 1 1/8 inches from the gasket seat on the valve with the gasket removed. If the pintle has a slotted shaft, you must exert pressure on the pintle and pull it up or press it in while rocking it side to side to adjust the height. If it has a smooth round shaft, use a dinner fork inserted into the spring to press it down and away from the pintle. Screw the pintle up or down to adjust to the correct height, then release the spring, being sure it fits into the slot on the bottom of the pintle. A gasket must be used on the IAC.
A_Lonely_Potato SEP 02, 10:10 PM

quote
Originally posted by fierofool:

That port with the orange cap should have a hard plastic line attached to it that runs over to the EGR solenoid. It should never be left open as it allows extra air into the combustion system. It can cause a high idle.



The previous owner(s) completely removed the EGR system. I will put that cap back in place!


quote
Originally posted by fierofool:

If you're messing with the IAC, the adjustment height of the pintle should not be more than 1 1/8 inches from the gasket seat on the valve with the gasket removed. If the pintle has a slotted shaft, you must exert pressure on the pintle and pull it up or press it in while rocking it side to side to adjust the height. If it has a smooth round shaft, use a dinner fork inserted into the spring to press it down and away from the pintle. Screw the pintle up or down to adjust to the correct height, then release the spring, being sure it fits into the slot on the bottom of the pintle. A gasket must be used on the IAC.



Hmm I didnt try really forcing the pintle, I only gave it some light pressure and it didn't move. I was going to try a method I read on here for blocking the IAC hole with my thumb to see if the ECM moves the IAC pintle at all. I will try both tomorrow if i get the time.


quote
Originally posted by Patrick:

...If that vertical orange thing in your photo is the "cap" you're referring to, it has nothing to do with the IAC valve.



fierofool mentioned that as well, I am obviously new to this engine haha.

skywurz SEP 02, 10:58 PM
The two threaded holes you focused on are for the throttle body heater. Its a common delete.
Patrick SEP 02, 11:31 PM

quote
Originally posted by skywurz:

The two threaded holes you focused on are for the throttle body heater. Its a common delete.



Let's not confuse the spud. One of those holes (the far one) in the photo is indeed for the TB heater, the other hole is where the IAC valve assembly unscrewed out of.

[This message has been edited by Patrick (edited 09-02-2021).]

Patrick SEP 02, 11:43 PM

quote
Originally posted by A_Lonely_Potato:

I was going to try a method I read on here for blocking the IAC hole with my thumb to see if the ECM moves the IAC pintle at all.



If you're planning on applying power to the IAC valve while it's removed from the TB, be very careful. I did that several years ago and lost the pintle when it shot off into the lawn!
skywurz SEP 02, 11:58 PM

quote
Originally posted by Patrick:

Let's not confuse the spud. One of those holes (the far one) in the photo is indeed for the TB heater, the other hole is where the IAC valve assembly unscrewed out of.




Awww fak too many gin and tonics too night I was mistaken. Thx for keeping me honest Patrick!
A_Lonely_Potato SEP 03, 09:49 AM

quote
Originally posted by Patrick:

Let's not confuse the spud. One of those holes (the far one) in the photo is indeed for the TB heater, the other hole is where the IAC valve assembly unscrewed out of.




Yeah the TB heater line is gone lol. There are quite a few things previous owners decided to do that I am finding. Should that hole be plugged or leave it as is?


quote
Originally posted by Patrick:

If you're planning on applying power to the IAC valve while it's removed from the TB, be very careful. I did that several years ago and lost the pintle when it shot off into the lawn!




Yikes, would it be safe to block it with my hand or does it come off with some power behind it?