I have a 93 5spd Altima and it runs really great. Most of the time the car idles fine, but every once in a while, the tach starts to dip down while idling. This has even caused the car to stall on a few occasions, but once I restart the car, it'll run fine. This seems to only happen once my engine is warmed up. I figured it wasn't any sensor because this doesn't happen all the time. Does anyone know what could be wrong?