Fast Idle Control Device (FICD) Solenoid
WARNING: This page is about a different car, the 1995 Nissan 200SX. However, it is still accessible from the selected car via links, so may be relevant.
Disconnect FICD solenoid harness connector. Apply battery voltage across solenoid terminals. If solenoid does not operate, check for sticking plunger or broken spring. If plunger and spring are okay, replace solenoid.