rookie brings up a good point and also jars my memory of a "glitch" with holley, IDK why but half the holley efi is pinned wrong on iac and iac doesnt wont do anything because the wires come pinned for a Chrysler iac vs gm and needs wires/pins switched fwiw. So ID determine if iac is even doing anything before getting too crazy with anything else. IF its IS working, since its takes like 30 seconds to rezero tps on a holley, IF you have a mechanical stop id do all my adjustments THERE before rxring tb to drill it repeatedly, Smitty
https://forums.holley.com/forum/holl...ndom-questions

unless we're using a holley TB with a built in IAC we have to swap two wires around on every holley IAC plug we use.
swap purple/white with purple/blue.

This is good info from you guys, I have been starting to talk with my builder about new 540cu long blocks and using most of my 500EFI ass, including the intake with Holly EFI. Sounds like we will run into the same issue.

Thanks, what OSO used to be like!

Rookie,

When you say “fix”, do you mean physically replace or make adjustments in the Holley software?

Thanks. Brad.

he means wire the iac properly so it actually functions. read above.
Just because the computer is calling for it to be at 100% doesnt mean it actually is
Unplugging it would confirm or deny what me, arctic and rookie are telling you

Johnny,

Thanks. Forwarded all this to the builder. Like I said previously, he has worked on several Merc 496’s and he’s worked with the Holley stuff, but this is the first time marrying the two.

Thanks. Brad.

Exactly what TeamSaris said.
Post 191 and 196 in my thread.
Holley HP EFI conversion

Rookie,

I will look at my connector and see where we are. This sounds like something even an experienced builder that has never dealt with it might miss.

Just to be clear… The Merc IAC is actually a Ford part, and I haven’t heard/read any reference to Ford here. Same/same?

Also…. The builder has mentioned the use of a stepper IAC vs the PWM (I guess???) type Merc uses. I understand the Chrysler IAC is a stepper. Would I be better off just getting a Chrysler IAC? Is it just that easy? Are they interchangeable, as far as the physical mounting and connecter?

I’m definitely into solutions that don’t require permanent alterations to relatively non-replaceable parts.

Thanks. Brad.

Hey Brad I have an idea.. why don`t you just switch the wires before you go off the deep end again.
Or verify that the IAC is actually opening.

Heres another tidbit, when you set up your closed loop learn, compensation, leave it turned off at first, manually tune idle, part throttle etc on the dyno. Once you get it close manually, let it auto tune CAREFULLY watching your learns, afrs etc, manually transfer them to the tables ONLY if they make sense and arent huge numbers or youll be chasing your tail, killing plugs, washing rings. all this holley stuff comes with those tables pre-populated at 100% or 50 % (Id have to look) but thats too much, the slightest false lean and youll be rolling coal, the most I let them learn is 25% while on dyno while i watch the afrs during pulls on my computer. In vehicle I never let them learn more then 10% fwiw. When we dynoed Rookies 454s we were still learning this and killed plugs, 02 sensors so fast it wasnt funny, Smitty