I know this was discussed before a month or so ago, but I've been searching for the past hour with no luck. I wired up a toggle switch to my cooling fan. When I turn it on the idle will drop about 100 rpm. Most of the time, turning the fan off will not bring back up, or at least not as quickly as turning it on. Press on the gas and it's back to normal. What would cause this? Is it something to worry about? I'm thinking/hoping that maybe I just made a crappy connection where I spliced into the ground for the fan relay..

 

on tpi cars, there's a valve on the throttle body that allows the computer to let extra air enter the engine to compensate for added load.