1. Check Electric Throttle Control Actuator Visually

WARNING: This page is about a different car, the 2004 Nissan Maxima. However, it is still accessible from the selected car via links, so may be relevant.

Remove the intake air duct.
Check if a foreign matter is caught between the throttle valve and the housing.

OK or NG

OK: GO TO 2.
NG: Remove the foreign matter and clean the electric throttle control actuator inside.

Fig 1: Check Electric Throttle Control Actuator Visually

Courtesy of NISSAN MOTOR CO., U.S.A.