Car ran fine then the alternator went out. Replaced the alternator and now the car won't start on the first try but does on a second try. Then it revs itself. The battery had been disconnected for 2hrs while I worked on it. Why would this be happening
The Engine Computer lost its memory and has to relearn "minimum throttle" before it will know when it must be in control of idle speed. It also might not give you the normal "idle flare-up" to 1500 rpm when you start the engine. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals.
To get it started, just hold the gas pedal down 1/8". You'll also have to keep your foot on the pedal at stop signs until the relearn is done.