1. Check Electric Throttle Control Actuator Visually

WARNING: This page is about a different car, the 2004 Infiniti M45. However, it is still accessible from the selected car via links, so may be relevant.

Turn ignition switch OFF.
Remove the intake air duct.
Check if foreign matter is caught between the throttle valve and the housing.

Fig 1: Visually Inspect Throttle Valve For Foreign Matter
Courtesy of NISSAN MOTOR CO., U.S.A.

OK or NG

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