Okay, we had a Jr supercharger on a gsr in a civic hatch. The day before we took the charger off, the idle starting fluctuation between 900 and 2000. Now in the morning, the idle will go to about 4000 for about 10-15 seconds, then drop to maybe 2 or 3 thousand, once the motor is warm it will go to 900 to 2000. We bleed the coolant, changed the idle air control valve, and there is NO check engine codes. Trying to make sense of it. any suggestions?

 

I had this problem (minus the jrsc). I traced the source back to a cracked vacuum hose fitment tube on the intake manifold. The moral of this story is: check all your vacuum lines and listen for a hissing sound (aka vacuum leak).

Also accidentaly switching the map plug with the tps plug can cause this problem as well. Both plugs are the same. Um... yeah I did that one too...