Manual Control Over IAC?

[Terrorist 5.0]

Ok everyone, after work today I took off my IAC, back-probed the ground wire, and gave the IAC ground. The results are on video, and until I figure out a way to attach said video, I will explain my findings. My theory above appears to have been correct. With the key on, the IAC receives power at all times. When given a solid ground instead of a pulse, the IAC opens 100 percent, effectively unlimited duty cycle. This should make it really easy for me if I only want one setting, that setting being 100 percent. I have not tried probing the IAC ground while the vehicle was running to see how that would go, in fact, the idea came to me on the way home. I may try that tomorrow. Now, there is a way to mechanically tune the RPM jump using the IAC. I could make my own restrictor plate with both holes shrunken down and experiment with that, but I want to do this the fun way. I need to figure out a way for a couple different settings. With this new information, does anybody have any ideas? I know it can be done, there is a video on YouTube explaining and demonstrating it pretty well, but that seemed somewhat complicated.

 

[lwarrior1016]

I remember there used to be a spacer plate that would go in between the IAC and its mount, and had a smaller than stock hole in it. Then there was a set screw that protruded in to the hole to block off airflow, but adjusting how much that screw went in, changed how much air was blocked.

 

[ttocs]

https://lmr.com/item/LRS-9939F/mustang-idle-air-control-iac-adjuster-efi-86-93-5-0?utm_source=google&utm_medium=cpc&adpos=&scid=scplp&sc_intid=&gad_source=1&gclid=CjwKCAjwmYCzBhA6EiwAxFwfgNwGJh5IKOzotQNhF8cGCfS9AT7SyXUMpFWKHd0B7-hdTk0UVtftDRoC7KIQAvD_BwE

 

[Terrorist 5.0]

I remember there used to be a spacer plate that would go in between the IAC and its mount, and had a smaller than stock hole in it. Then there was a set screw that protruded in to the hole to block off airflow, but adjusting how much that screw went in, changed how much air was blocked.

Yes, these are still sold actually on LMR, they were designed for Foxbodies as a bandaid fix for carbon buildup, but some people said it solved their surging idle with their cams. Beats me, but looking at it, I don’t think it would restrict enough airflow to get what I’m trying to achieve.

 

[ttocs]

I had one with I used a proproduct tb that caused it the rev hang and it worked. Took 5 mins to adjust it

 

[Terrorist 5.0]

I had one with I used a proproduct tb that caused it the rev hang and it worked. Took 5 mins to adjust it

The rev hang is not a result of the throttle body though (mine is stock), it is programmed in the ECU for emissions. It burns off any excess fuel by letting air in when you let off the gas.

 

[ChrishCatania]

Hi everyone. Everyone knows about the rev hang in these cars between shifts. For some people, this feels normal. But for me, it was unbearable, especially since I learned to drive on older (some carbed) cars. To remedy this, I unplugged the IAC. The car drives amazing now, but cold starts are a little interesting. The car runs really rich because of the lack of air from the IAC, and likes to surge and stall unless I pedal it for sometimes a second or two, to a full minute or more at times. I have a new IAC on the car already from when I tried the IAC restrictor plate (which didn't work), and I think it should be put to use. Has anybody ever wired in a manual control for the IAC? I only need it to be on/off (it is pulse width modulated if I am not mistaken so I should really be saying 100/0% duty cycle), just so I can have a somewhat peaceful cold start instead of pedaling it. If anybody has done that, please explain what you did, or if nobody has done it, please feel free to spitball some ideas. I would love to hear it.

My advice would be to get a separate temp switch (amazon) that you can set to activate a relay at 160* engine temp, and then have the relay open the IAC circuit. IIRC, with an open circuit the IAC is only open 20%, which would make a big difference. If thats not enough get an old solenoid from a dishwasher (usually 1/2" NPT) and plumb that just before the IAC so that the IAC only has access to air when the car is cold in the same manor I mentioned above.

 

[Terrorist 5.0]

My advice would be to get a separate temp switch (amazon) that you can set to activate a relay at 160* engine temp, and then have the relay open the IAC circuit. IIRC, with an open circuit the IAC is only open 20%, which would make a big difference. If thats not enough get an old solenoid from a dishwasher (usually 1/2" NPT) and plumb that just before the IAC so that the IAC only has access to air when the car is cold in the same manor I mentioned above.

That’s not a bad idea at all, but with my current setup, I can idle it up whenever I want. Great for underdrive pulley undercharging problems.