I just bought a 93 Firebird from an auction it has a 3.4L engine when I bought the car it was idling high (2000 RPM’s) there are no engine codes, It has a new throttle control valve , throttle position sensor and coolant temperature sensor I checked for vacuum leaks and can not find any . Today I disconnected the battery for 10 min when I reconnected and started the engine was idling at 1000 RPM’s in neutral and 8000 RPM’s in drive when I revved the engine to 3000RPM’s and released the accelerator it would fall to 1500RPM’s for about 15 sec and fall back down to 1000RPM’s when I turned the engine off and started the car it went back to idling at 2000 RPM’s I disconnected the battery and repeated the process and everything worked the same way……any idea why the car wont idle correctly?