Idle Hunting

[ACPMick]

Hi Everyone. I have 90 z32tt with a 4G+ pnp. I am basically just finishing my build so it has not seen the street yet. Also please keep in mind that I am new to link and aftermartket ECUs in general. I took my car to a tuner last week to have it dyno tuned. I don't yet know how the drivability is since I am waiting for my front bumper to come back from paint. So far I had let the car idle a couple of times to look at some minor issues (small collant leak) which I have fixed. Here is my issue. 

When the car is cold started it starts nice and stable and come down to around 1200 rpm. Then it sits like that for a while if I blip the gas at all it goes to about 1900 and stays there. Eventually it comes down to about 900-1000. At that point if I touch the throttle it comes down to about 1100 then it starts hunting until 10 to 20 seconds later it calms down to 900. Is there anything I can do to make this a little more stable. I have attached two logs. One is at it sits up high and the second is where its warm and hunting. TIA. Please let me know if there is anything else I need to add. 

Log 2020-09-9 12;09;57 pm.llg Log 2020-09-9 12;17;36 pm.llg

[Adamw]

There are at least two problems; 

1. Either the throttle is open too far or there is a big leak.  Right after start up the closed loop idle control has fully closed the idle valve trying to bring the idle down but it is still sitting 200RPM above target with the valve fully closed.  So assuming the idle valve does actually work this means the air is coming from somewhere else.
2. It doesnt look like idle control has been tuned at all.  The rev hangs after the blip because the idle valve jumps to 48.5% which is the value in your base position table.  Obviously if it cant reach target with the valve fully closed - then its definately not going to reach target with the valve open at 48%.  This at least suggests the valve is working.  Because the RPM then goes above the RPM lockout the closed loop idle control will not try to close the valve on its own.

So, fist step is to unplug the valve with the engine running, then set up the throttle so that the idle speed is somewhere about 100RPM lower than target.  This will give you a good place to start tuning the base position table from.

[ACPMick]

Thanks for reply. I took out the valve and cleaned it and deleted the air regulator which the ecu doesn't utilize anyway. It did get better so the air regulator was definitely a source for a vacuum leak. It now seems to idle around 900 when warm. I will post a log tomorrow. It is still hunting a bit but not nearly as bad. Now my biggest problem is that when you close the throttle the rpms go just a little too low (500) before they recover to about 1000-1100 for couple seconds and then return to 900. As well I am running a separate controller for the e-fan so I need to figure out how to tell the ecu that the fan is on for step up.