I am still fighting this idling issue. The car idle's at 1250 RPM in Park/Neutral and like 1000 RPM in Drive. I have checked everthing... Out of curiousity, I unplugged my IAC connector and drove around all day. The car drove EXACTLY like it did when it was hooked up!! Does this mean my IAC is bad?

Also, whenever I am driving down the road and let off the gas... SOMETIMES and ONLY SOMETIMES the RPMs will fall right back down to idle... other times, they back back off slowly like they should do. Could this problem be related to the above mentioned issue?

-Thanks

 

Try cleaning the IAC and the idle passages in the throttle body.

 

Unpluging the IAC connector will simply leave the IAC pintle in exactly the position it was in when you unplugged it. If that means it was admitting enough air to idle the engine at 1,500 RPM, that's just exactly where it will stay.

What you really need to do to diagnose it is follow the prcedure for throttle minimum air positon adjustment. If you cannot get it to idle down with that procedure, you need to completely remove, disassemble, clean, lubricate, and reassemble/install the IAC. Then you'll be able to check and set minimum air position.

Simply unplugging it while running is doing essentially nothing.