ok no air leaks found
do the ISC is bad
only the ISC is the path of, air flow. on a hot engine, if all leaks are gone ,ISC is bad. (stuck)
keep in mind all engines, Vacuum plenum,love to find leaks, and do, and will suck air, by any means it can,,, and lots of ways there are, even injector cushions leak.
do you have the device i showed you>(cold start fast idle
SEE this, but if the stops are ok,, (this device, raise the stops)
http://fixkick.com/IDLE-AIR/Sport-IAC.jpg
so ISC is bad, stuck or just needs cleaning its and electromagnetic(motor) driven air valve.
they fail, easy, with EGR gasses and PCV gasses from H3ll there. all do.
the ECU told you,it cant control idle
The RPM guage,shows 1200, tell you it can control idle
that means air leaks
aka, vacuum leaks same thing.
if the plenum has no leaks, (normal hot ) then only the ISC is the 1 and only air supply, and is failing)'TV closed 100%
I pinch all vacuum hoses, at failed 1200rpm to see who leaks(now) and who does not.
finding gasket leaks more hard.
even egr, isc base gaskests can leak, or seen MISSING.
so can injector base cushion(or 0ring base side)
even TB base gasket bad
even brake booster diaphram cracked
the ISC test, might work
remove it.
keep plugged in,
key on 3 times and person 2, looks at iSC guts
it cycles, 1 time. to reset it self.(software)
if not its jammed. check is coils yet for same ohms,? 10-15ohms, my guess.
800rpm hot
900rpm hot a/.c on
1200 is dead wrong.hot if really hot.
i dont think any J18/20 engine has TB bleeds screw, i thing the ECU does all that magic. (has more dynamic range)
likes
real suzuki j18
http://fixkick.com/engine/18L/18L252.jpg
j18 idle too high page
http://www.fixkick.com/IDLE-AIR/J18-idle.html