Hi all, new to forum hoping someone can help me. I have a 1999 civic ex automatic that has an erratic idle and will stall sometimes on deceleration. It has a code p0505. The idle will race up to 2000 on startup and fluctuate rapidly until check engine light comes on then will idle steady but still high. It seems this all began when i put on a/c one day but could be coincidence. Please, any info will help greatly.