I was talking to a buddy of mine yesterday and the subject of IAC's came up. Now he races on the dark side (mustangs) and he told me that a lot of them have to upgrade their IAC's to an aftermarket higher flowing one. I've never heard of this.
Is there any truth/benefit to this or has he been using his nitrous bottle for his own personal enjoyment?

 

I'd like to see the parts.

There may be some advantages to changing to a different IAC "IF" the factory one is too slow or too limited to make adjustments for a highly modified engine. An engine where the idle is choppy due to the cam profile and requires a lot of attention to maintain a steady idle control value.

 

Yeah. I'm "slightly" built. Chasing down my idle issues is proving to be more difficult than anything else i've had to deal with.
Even messing around with my programming isn't really helping all that much.

 

Never heard of it. There are some stuff you can do to calm down the idle with a hot cam depending on code in PROM.

 

I'm not trying to eliminate my lope, i'm trying to eliminate a surge. THAT's proving to be difficult.

 

Hey so did you ever make the 490 some hp that you thought you would make with long tube runners and a 355? Hadn't seen anything on that. I can tell you went with a 383 but those power numbers would be tough as well with LTR's. Just curious

 

I would think any slowness in reaction would be more from the ECM's ability to respond to the sensor input and figure out how to hold a stable idle. The IAC itself is a stepper motor and can react about as quickly as the ECM can throw an open or close command at it. A typical "rolling" idle is actually going up and down rather slowly, by computer standards. And the IAC shouldn't need to "chase" the idle RPM very much- with proper programming the IAC shouldn't need to move very much at all. But if the ECM can't handle the idle conditions it's faced with it'll overshoot one way, the idle RPM with change and then it'll overshoot the other way, causing the idle to roll like that.

 

ford IACs are quite different from what GM uses. a ford IAC is nothing more than a solenoid that controls an air valve. if you unplug it with the motor running, the motor drops to base idle right away & most times it will
probably die.
ford started using what they called sludge tolerant throttle bodies, they said you could not clean them, if you did the TB would be damaged. they would sludge up so bad, the IAC couldn't control the idle speed. this caused problems with low idle speeds which also started causing the motor to die. their remedy was plate with 1 or 2 set screws in the side of it that was mounted between the IAC & throttle body, all it did was to allow air to bypass the IAC.
with some of the better ideals ford has had, i would tend to believe your friend.

a few truths about fords.
all fords are already broken down, they are just looking for the most inconvenient time & place to quit.
the only real way to fix a ford, is to replace it with a chevy.
put a mechanic to work, buy a ford.
and remember, friends don't let friends own fords, unless they aren't really friends.

 

Nope. Ran the engine lean and melted a hole in slug #3 on the 350. The 355 is in the Formula, my daily driver. Forgot that in SuperAUJPv3 that the rpm limiter was sky high. Had to align hone. Now it's a 383 with all the same parts. The 383 actually is a slightly better match for my cam. It brings the power band down some.
Haven't made it to the dyno yet. I'm still combating this surge. I have been able to break the tires loose at 57 mph though. That was fun.

 

Yeah that can be fun and scary when the tires come loss on a downshift. What pcm are your running? Maybe time to save towards an aftermarket ecm if your are still trying to burn chips for a 749. Good luck though.

 

I'm using the stock 730 ECM with a "few" programming changes.

So I guess this whole aftermarket IAC thing means nothing when it comes to GM's.
Good to know.

 

Well for me my stock pcm with mass airflow was not up to seriosu mods above 400hp. I am trying to finish up a 411 swap but proving difficult to find someone to modify my distributors.