ok, got a type r in my 5g, p28 ecu, jdm header...
the problem: car is possessed. sometimes the idle is fine, sometimes it goes up and down and throws a code (01= 02 sensor)>when i try to shut the engine off and start it back up, the light goes away. i've already tried 2 o2 sensors, one from a gsr, one from jdm type r. could a faulty o2 sensor cause the idle fluctuation? i've already checked vacuum leaks at the intake area by spraying some carb cleaner, it seems ok. i just need all the help/suggestions i can get right now. thanks

 

vet a voltmeter and check the wiring on the o2 sensor
make sure its not grounding out anywhere and check all connections.

if thats not it, swap ecu's it could be a bum ecu.

 

I'm with Kamin here.

BUT, I got one more question.

Did you chip the ECU? If so, which program?

Also, check your grounds at the thermostat. Sometimes they look OK, but they are heavily corroded.