ok guys hopefully someone can anser this question asap i have a 90 si with a d16z6 swap and they dont have a thermostat housing sensor plugged in at all which im pretty sure is causeing my surge idle going from 200 to 1500 also have a bad head gasket which could also be it! but idk how to run the wires for the sensor can someone please help me!

 

the wiring for your fan switch is on the back of the engine where the sensor would have been on the stock engine. you should see wires chillin back there that look like this.



extend those 2 wires over to the thermostat area, add an appropriate connector, and plug it in. your radiator fan will now kick on like it's supposed to.


as far as the idle goes, it could have to do with the iacv or fitv, but i wouldn't bother messing with those until you get the heasgasket fixed since it is likely the cause of hunting idle.