I have a 1993 modified rx7 and have engine idle hunting/surging. I looked on numerous posts and it seems no one has come up with a definite answer. I have a power fc and commander, ported motor, intake and exhaust, 850cc injectors, and some other minor things...It surges between 1000 and 1600 rpms and stabilizes after about 30 seconds or so if I don't touch the gas. When I come to a stop light, it will do it again. The a/c being helps to stabilize it. Any help?

 

Check the settings in the PowerFC. It sounds like there are some idle bins that are too lean, causing the hunting. When you activate the A/C, the engine loads up and reads from a different area in the fuel map which is tuned a bit richer.

 

ok will do thanks