Wonder if your IAC is sticking?? I dealt with that with mine, just happened to have another IAC laying around installed that and Idle tuning was 10x easier. Also try enabling spark timing that was the only way I could get mine to not hunt.

Also timing table will have an effect on it. If for say it idles at 1300rpm at 10 degrees then at 1600rpm(rough guess) it goes to 20 degrees that will cause it to idle high.

 

The IAC is brand new, had one stop working on me on dragweek last year so i replaced it with one from NAPA. I also have spark timing enabled, when the idle hangs at 1800rpms, it isnt pulling timing though.

Jeff, a few years ago I had a similar problem on a customers car. We were using GM IAC valve. It was wired backwards. When we wanted 0% it was actually giving us 100%. Check the pin out.

I have the similar problem with my idle screw, way too touchy! Doesn't take much to swing the idle up or down a few hundred rpms with barely moving the screw. It only adjusts the primaries.

I will check that out, thanks Mike.

Not sure if this applies to your combo or not, but have you tried setting the throttle blade so that your IAC reads beteeen 2 and 5% as stated in the instructions? Let it do its thing until it gets to operating temp, shut it down, put a quarter turn into the idle screw. Perform TPS reset and see where you're at. Still zero? Repeat the same process. Over 5%? Shut it down back the idle screw off an 1/8. Perform a TPS reset, fire it up and see where you're at. You get the idea I'm sure. Then you'll be able to set your idle speed through the Holley software. Just remember you have to do a TPS reset any time you turn the idle screw. Sorry if you already knew or did this. Just throwing it out there.

What i usually do is get the IAC to 0% then unplug it, then i set the idle screw when the engine is hot, so that the IAC has no influence. I do need to do a TPS reset though, the TPS, with my foot off the pedal was reading 0.7% last night, but i figured that being under 1% wouldnt make much difference...

 

Jeff, a few years ago I had a similar problem on a customers car. We were using GM IAC valve. It was wired backwards. When we wanted 0% it was actually giving us 100%. Check the pin out.

I have the similar problem with my idle screw, way too touchy! Doesn't take much to swing the idle up or down a few hundred rpms with barely moving the screw. It only adjusts the primaries.

 

Check for binding .

Put a heavier return spring on it . It needs a return spring just like a carb .

It must return to zero or your just chasing your tail .



Hold Position :

Description: Position the IAC motor will “hold” or “freeze” at when the TPS moves above idle (when TPS becomes greater than 0%).




2% is what they recomend you start with when adjusting throttle blade position ( curb idle screw )

You back the idle screw out until the blades are all the way closed ...... do TPS auto set ......adjust blades until you see 2% on the TPS ......... do TPS auto set again .

I'm glad I found this info! I had to repin IAC plug from GM to Holley IAC. Thanks!

 

Not sure if this applies to your combo or not, but have you tried setting the throttle blade so that your IAC reads beteeen 2 and 5% as stated in the instructions? Let it do its thing until it gets to operating temp, shut it down, put a quarter turn into the idle screw. Perform TPS reset and see where you're at. Still zero? Repeat the same process. Over 5%? Shut it down back the idle screw off an 1/8. Perform a TPS reset, fire it up and see where you're at. You get the idea I'm sure. Then you'll be able to set your idle speed through the Holley software. Just remember you have to do a TPS reset any time you turn the idle screw. Sorry if you already knew or did this. Just throwing it out there.

 

I have a 4150 Accufab and it has stuck in the past . Make sure its not binding anywhere .

.7 will make a difference because the ecu doesnt consider that idle . So anything related to "idle" will be effected .

 

Let the timing control your idle speed. The IAC has little effect when using a larger cam. This has been my experience.

 

If TPS doesnt return to zero , the IAC will stay at the " IAC hold position " value .

 

So i made some changes to it tonight, here is what i started with tonight.

https://goo.gl/photos/6nwTdvRy8jkUKwDK6
https://goo.gl/photos/ekjEs292GFHu7R6b6
https://goo.gl/photos/qJTNBYiPNku1KJjeA

I got the car where it was idling great. Made some minor changes to the idle settings, but the thing that seemed to help the most was pulling some timing out of it(directly from the timing map). I went from 35 degrees down to 30 degrees, and that brought the idle down a bunch, and the holley was ramping a little bit of timing out to keep it running.

So i took the car for a drive and everything was great, kick the clutch in and the car is settled into a nice idle even before i come to a stop. Fantastic. It was as good as it ever has been, then i pulled into a parking lot around the corner from my house, and the car is doing the thing where it wants to die again, i let it go to see how long it would stay running, which was probably about 3-5 seconds. I fired it again and kept it running with my foot to see what was going on, before it was pulling the timing down to between 25-27 degrees at idle, now, i see it is up to 47 degrees timing trying to keep the thing running. So i went back into the timing map and added the 5 degrees i took out and it seems to be better, so i head home. Got into the garage, played with it just a little more and it is idling between 1300-1450rpm, which i am OK with, here are screenshots of what i have now, setting the IAC parked settings wide open across the board seemed to help with post start stumbles.

https://goo.gl/photos/s1SaXG5BzUDwSDY49
https://goo.gl/photos/UpF4LWE4RZ3m5Ayy5

Whats everyone think, am i headed in the right direction, or am i going to be chasing my tail with this thing?

edit, since no more photo bucket, i had to use google, but it won't post the photos directly to the thread, so you will have to click the links to see the screenshots.

 

Do you have learning enabled at idle? If so, turn it off. It'll jack up the idle area of the map. I like to disable idle timing control while tuning. While it's idling,watch the map, and whats going on with CL comp and tune the map manually until you get it as stable as you can, then enable idle timing. That high IAC parked position makes me think you have too much cranking fuel. What is your idle target AFR? Sometimes trying to get the wrong AFR to idle correctly will have chasing things.

 

Closed loop is turned off till 1800 rpm. I dont really target an idle air fuel, i try to tune it to where it is stable and not dumping raw fuel out of the tailpipes.

 

Dam.

 

Why is your IAC setting on Holley 4 Bbl MPFI ?

Accufab uses a GM stepper .

Anytime you adjust the blades , you must do an auto set .

 

Not sure why i didnt realize that. I will change that tonight.

When you pulled timing and then added it back does sound like you could have an intermittent issue with tps not return to idle. Will cause the IAC to stay at the hold position. Sorry if Im posting the obvious.

I thought that it was 2% and over where it held the hold position. The TPS now is at 0.2%, tried a few times to reset it and it keeps ending up there, honestly, i think most of the problem is with the throttle body. Being that it takes such little adjustment to throw it off, i think where it shuts may vary. in the past i have been able to change the idle by pushing down on the front of the linkage and it would close the throttle slightly and move the idle speed. It may not be consistently shutting, or maybe when it heats up the tolerances get looser.

 

When you pulled timing and then added it back does sound like you could have an intermittent issue with tps not return to idle. Will cause the IAC to stay at the hold position. Sorry if Im posting the obvious.

 

Check for binding .

Put a heavier return spring on it . It needs a return spring just like a carb .

It must return to zero or your just chasing your tail .



Hold Position :

Description: Position the IAC motor will “hold” or “freeze” at when the TPS moves above idle (when TPS becomes greater than 0%).




2% is what they recomend you start with when adjusting throttle blade position ( curb idle screw )

You back the idle screw out until the blades are all the way closed ...... do TPS auto set ......adjust blades until you see 2% on the TPS ......... do TPS auto set again .

 

Heres the difference .



Holley (Chrysler) IAC stepper motor pin-out with flat connector:
Use a magnifying glass to see the four IAC connector cavities - designated A, B, C, D.
These letters are located where the wire seal retainer clips to the connector body.

The four wires are A: purple/blue "A LO", B: purple/black "B HI", C: purple/white "B LO", D: purple/yellow "A HI".


General Motors (LS, LT, etc.) IAC stepper motor pin-out with flat connector:
Use a magnifying glass to see the four IAC connector cavities - designated A, B, C, D.
These letters are located where the wire seal retainer clips to the connector body.

The four wires are A: purple/white "B LO", B: purple/black "B HI", C: purple/blue "A LO", D: purple/yellow "A HI".






.

 

Thanks for that, no wonder the TB from Holley doesnt work right, it uses a chrysler IAC installed on a LSX harness.

 

Holley LSx Terminated harness is for GM IAC
Holley Universal Harness is pinned for the Holley/Chrysler and for whatever dumb reason the IACs are identical looking.

 

Well this is great info, thanks guys. I have an unterminated harness in the car that i did with a friend, and we used the MPEFI schematic as a guide, which may have had to somehing to do with my IAC setting choices. I am going to repin it now.

 

Repinned the harness for the GM IAC, and everything is good now.

 

Nice. Glad you got it figured out.

 

Glad you got it, I had the exact same issue. The holley harness is pinned for a Chrysler unit instead of Gm. It drove me nuts for months until someone told me.