I have an automatic, 1997 Mazda 323. It would start fine however, the rpm would go up to 2500 and will stay there for a while. When I shift the gear to Reverse or Drive Mode, rpm would go down to normal. However, when I shift it back to Neutral or Park mode, the rpm would again go up to 2500. It will stay on that state for several minutes but once I drive it off and the engine warms up, it gradually lowers the RPM to about? 750 RPM. It's quite alarming since I think this would make the car use up more fuel. Hope you could help. Thanks in advance.
I had the alternator, ignition coil and cerbo kit checked, and according to the mechanic, there's nothing wrong with them. Also, the ignition and cerbo were cleaned.