I'm pretty green to tuning so be gentle.

I have a freshly assembled and running full bridge engine, and I'm trying to really hammer out my cold starts and idle. The car likes to idle and "chop" at around 17-1800 RPM. No matter what setting I change it seems im chasing my tail on closed loop idle control. It may fluctuate (surge) between 2100 to 700 RPM, or as close as 1900-1600 RPM, depending on my inputs and selected targets. Idle will drop.. IAC will throw 100% at it.. idle will balance at ~35%... then suddenly drop.. repeat. What am I missing?

If I switch to open loop, where there aren't any corrections, it will have a clean idle in perpetuity.

 

Its a mission to achieve what you're asking for in the way you're doing it. The issue is, you will need to make timing adjustments in addition to what you're doing. This will give you the higher idle on initial start then after th 30 second timer, it will come down and settle out to the chop (as if it were stock). This makes for a pedal-less cold start.

Every car is different and without knowing what you're doing, it's not advised to just keep changing numbers at random. Also consider mechanically, you need to make sure your throttle body and tps are set correctly. You also need to know for absolute you have no vacuum leaks. You'd be surprised how easy this is to miss.

You also need to know your iac is actually functioning as it should. A LOT of them simply are just tired and you get what you get. Sometimes cleaning them out helps, other times, you just have to accept they age and function accordingly.

You're dabbling in a bit more advanced tuning techniques. Until you have a tuner physically present that is versed in this, it would be advised you just do what you stated works and leave it be.

 

When doing a cold start in open loop, its pretty dialed and can get a pedal free start. Doesn't sound great but after some temperature everything levels out.
In closed loop it will fire, get up to temp, but once it does, it starts chasing something or I have an input wrong. I can narrow the surging but not eliminate it.

I have tried multiple TB calibrations. (Its a 92mm GM cable TB) The car seems to like 3% on the TB, recalibrated to 0%.. but I've recal'd at true 0% all the way to 10% with no active IAC.

The IAC DOES seem to be functioning as intended. Its not OE to the car. It is a similar style Ford unit. I can hear a mechanical movement when the car is not running and I trigger it manually. When running I can make adjustments in open loop and see/hear changes. My "idle out" circuit is also giving me the feedback I would expect based on my inputs.
BUT.. I admit to being a novice, and being out of my element, but I like to figure things out. I may have to break down and rely on my local Haltech tuner friend.

 

If idle works fine in open loop, but it gets wacky in closed loop, my best guess is you need to tweak the settings the ECU uses to lock out/disable when closed loop idle control is active.

I'm not familiar with Haltech, but the Link G4+/G4X/G5's I've used all have several settings that work together to tell the ECU when you want closed loop (CL) idle control to be active, and when CL idle control should be disabled. For example, perhaps CL idle is disabled when RPM > 1500rpm, or MAP > 60 kpa, or vehicle speed > 5 MPH or something like that. The Haltech probably has similar CL idle lock-outs that you'll need to look into; likely what's happening is when the car idles normally it may be crossing one or more of those lock out thresholds, causing control to dither between open & closed loop operation.

With a bridge port, your normal MAP while at idle will tend to fluctuate more than it would with a stock port, so if there's a MAP based lockout on CL idle, that's the first setting I'd look for.

 

If idle works fine in open loop, but it gets wacky in closed loop, my best guess is you need to tweak the settings the ECU uses to lock out/disable when closed loop idle control is active.

I'm not familiar with Haltech, but the Link G4+/G4X/G5's I've used all have several settings that work together to tell the ECU when you want closed loop (CL) idle control to be active, and when CL idle control should be disabled. For example, perhaps CL idle is disabled when RPM > 1500rpm, or MAP > 60 kpa, or vehicle speed > 5 MPH or something like that. The Haltech probably has similar CL idle lock-outs that you'll need to look into; likely what's happening is when the car idles normally it may be crossing one or more of those lock out thresholds, causing control to dither between open & closed loop operation.

With a bridge port, your normal MAP while at idle will tend to fluctuate more than it would with a stock port, so if there's a MAP based lockout on CL idle, that's the first setting I'd look for.

 

I think you're right in the fact that there is a table somewhere with a "correction" that I'm not finding. To FDAUTO's point, I'm not a professional tuner, and I'm getting pretty deep in the weeds with this. It definitely seems somewhere I'm hitting a threshold value and things aren't happy. Ill have to triple check what tables/corrections are being altered in the closed loop state.

..or I leave it open loop and let it BRAP, while it eats at my soul that I haven't conquered some obscure setting.

 

:UPDATE: ..for the sake of education..
Patched in Chris at LMS-EFI, and we couldn't get any kind of consistency out of the inputs/changes we were making. At the end of the session the conclusion was "something isn't right".

I removed the IAC and positioned it so I can watch the actuation, manually sending it 0-100%DC on multiple frequencies.. nothing..

Pulled an FD OEM IAC out of mothballs and cleaned it up, made a pigtail and tested it the same way and voilą.. we have movement.. although admittedly.. not a lot..

Using the installed OE unit I can get the car to chase the idle around within a couple hundred RPM.. but time will tell if this proves useful on a full bridge or not.