I couldnt find what I was looking for but I did find some stuff on the Idle learn. I hope this helps.

The idle learn procedure must be done so that the ECM can learn the engine idle characteristics.

Do the idle learn procedure whenever you do any of these actions:

1 Disconnect the battery.

2 Replace the ECM or disconnect its connector.

3 Reset the ECM.

4 Remove the No. 6 ECU (ECM) (15 A) fuse from the under-dash fuse/relay box.

5 Remove the No. 41 BATTERY (100 A) fuse from the under-hood fuse/relay box.

6 Remove the PGM-FI main relay.

7 Remove the battery wire from the under-hood fuse/relay box.

8 Disconnect any of the connectors from the under-hood fuse/relay box.

9 Disconnect the connector (C404) between the dashboard wire harness A and dashboard wire harness B.

10 Disconnect the G1 terminal.

11 Adjust the idle speed

To complete the idle learn procedure do this:

Make sure all electrical items (A/C, audio, rear window defogger, lights, etc.) are turned off.

Start the engine. Hold the engine at 3,000 rpm without load (in neutral) until the radiator fan comes on, or the engine coolant temperature reaches 176

 

On another note, check for vacuum leaks!

 

would the idle learn and a vac leak set off an iac code tho???

 

Well like I said one problem could make somthing else act up and set its own code. So just cuz its an iac code doesnt mean its the iac, plus you did already replace the iac once and it still does it. The vacuum leak could make a abnormal idle. Though I dont have much hands on with the s2000, Im speak from general experience.

 

gotcha, i'll be sure to check for any leaks 2m, and i'll to the idle learn procedure, see what happens then i guess.
i highly doubt that both of the iac sensors are bad, but its possible

 

Good luck

 

Idle learn procedure will not help your problem.

Let's start with the actual code. (PXXXX)

Then we can proceed

 

P0505

 

DTC P0505: Idle Control System Malfunction
Warm it up and if the idle is still higher its saying to take the intake off, leaving just the throttle body. Then start it again and but block the upper and lower ports on the throttle body. If the engine stalls it is saying the iac is at fault. If it doesnt stall it has a list of checks for vacuum leaks.
PCV valve
PCV hose
EVAP canister purge valve
Intake manifold
Throttle body
Brake booster hose
Hope it helps

 

fixed the problem, ended up being a leak in my catch can which basically is the pcv system. thank you so much for all your help guys, i appreciate it