Long storyshort. My Go-Autoworks turbo kit is installed and the car is just about ready for the dyno. I've got a DW200 fuel pump, skunk 2 4bar MAP, and HunterTuned 1000CC injectors, AEM wideband, s300v3, 3 inch stainless exhaust. I'm working with my tuner remotely to get a base tune setup. However we're running into a weird issue where after the car gets warm it starts to hunt/surge. The IACV was replaced last year, and I just cleaned it out again to be sure. It seems to be working fine, as I've gone through the process of unplugging it and adjusting the idle screw until its around 500rpm then plugging it back in and moving the duty cycle slider to the middle.

If I run with closed loop on, with a set voltage target that is roughly equals 13.5 AF, it runs perfectly at the 950rpm as I've set the idle in SManager. However with closed loop off, the engine hunts from 700-1300 rpm after its warmed up. What's weird is that for the first 2-3 minutes of running, its fine, but then as it gets warm it start to hunt.

I've done a smoke test, zero leaks.
IACV is new, and seems to be working.
I've tested with and without my Fast Idle Thermo Valve (i put a block off plate in its spot with a gasket and re routed the coolant lines to just the IACV and not the FITV. This literally made zero change to anything)
Playing with the IACV duty cycle, target rpm, or anything else doesn't seem to help. It just makes the hunting more or less aggressive or shorter/longer.

Here is a link to my current tune and a 4min datalog. The idle is rough for the first minute or so, but then levels out. You'll see around the 3 min mark things start to get weird and the engine hunts. The only thing that instantly solves the issue is turning on closed loop. To me it sounds like a fueling issue. https://drive.google.com/drive/folde...qd?usp=sharing

Any ideas? I'm running out of things to check. Thanks for any help you can offer.

 

I am kinda dealing with a similar issue but then it dies. Taking a look at your log now. Weird how nobody has jumped in on this. Your post is Feb - any resolution?

 

After IACV #4 I bought another one but this time it was $200 instead of $100. Issue went away. I had good, functioning, clean IAC valves that in every aspect of bench testing were perfect, but ultimately were the issue. Who knew, cheap products suck

 

Good parts ain't cheap... and cheap parts ain't good.