[konafocuswrc]

after sct chip taken out, driven for a week..
was running perfect until yesterday..
then engine code shoed up finally, it shows P1506..

P1506 - Idle Air Control (IAC) Overspeed Error This DTC is set when the PCM detects engine idle speed that is greater than the desired rpm. IAC circuit short to GND
Damaged IAC valve
IAC valve stuck open
Vacuum leaks
Failed EVAP system
Damaged PCM
Disconnect IAC valve and look for little or no change in engine rpm as an indication of a stuck or damaged valve.

but i still cannot find out what this causes..
this got nothing to do with misfiring right?
when misfiring happens, idle speed is rough and sticks a bit..
idles rough(misfire), then in few seconds jumps upto 1000rpm and slowly goes back down to 750~800..