I have a 1999 V6 Mustang that I got in June, and I've had no problems with it up till now. Usually my mustang starts idling high, then drops to between 750 and 1000 rpms. Last night I took the dash apart, and before I did, I disconnected the battery (not sure if this is relevant), and now when i start the engine, it drops quickly to below 500 rpms, almost to a stall, then it revs up and down. (Sounds like i'm revving my engine). After a minute, it goes away and seems to be just fine... But when i turn it off and start it again, it repeats the same thing. Any help would be greatly appreciated.. since i'm not exactly great with cars. Thanks.