SomeYahoo

First post, likely to get something wrong, but here goes.

Just got my short nose crank 1.6L up and running with a GT2860 (churbo). It will usually idle decent initially (still tuning out some hunting) but after it is fully warmed up, it will sometimes run, sometimes die at idle. With throttle or boost, it runs great and pulls hard. Hoping the experts here can help to figure out what's up with my idle. My specs:

1.6L SNC engine with a loctite crank pulley fix (base timing is solid at 10*)
Flowforce 720cc injectors
DW200 fuel pump
Kraken exhaust manifold
2.1/2" downpipe to 3" resonator and downturn
Small intercooler, custom piping
GT2860 churbo, TBD on the wastegate (hit 200 kpa so far)
Coolant reroute
Turbosmart kompact BOV
AEM 30-0300 X series wideband
GM IAT
MAP sensor onboard

Current tune and log file showing some runs with intermittent idle issues throughout (including a couple of bump starts along the way) attached.

Thanks in advance for any help!

SomeYahoo

Well, no replies so far but I'm continuing to fight this issue. What I've done:

Set all idle cells to the same value and locked them
Full boost leak test, corrected two leaks (IAT bung and a loose MAP line). No leaks now, so no vacuum leak as an air source
Dead ended the idle air valve (the coolant temperature actuated one) with a full gasket to eliminate that as a source of air
Sprayed carb cleaner around and didn't get any idle jumps

To try to fix, I set the idle control to none and adjusted the idle air screw and to my surprise I can run the screw in 100% and it still idles. I've tried other idle control methods and have had similar results.

Bottom line question - what source of idle air am I missing? What else do I need to check?

Tune and idle log attached.

hedz0r

tried to open the tune, but unfortunately you didnt mention its a speeduino ecu. I dont have that firmware and most of this site does not use that ECU. I think most of the support for that ecu lives on facebook, maybe try the speeduino groups there.

SomeYahoo

Thanks for the reply. Forgot that they had different firmware and therefore you couldn't even open the tune. I'm running a SpeedyEFI unit.

Tonight's troubleshooting...

Re-ran a test to get min and max duty cycle. Found if I go below the minimum the idle goes back up, is that normal? As another check, I unplugged the valve and idle jumped up which also seemed odd. I thought when you unplugged the valve it closed? With it unplugged, I could run the idle air screw all the way in and the car still ran.

More research to do, but can anyone confirm that the IACV should fully close when unplugged?

SomeYahoo

Confirmed via Miata garage article - IAC is 20% open when disconnected. More testing to come.