Code P085, Idle Throttle Angle Too High: Notes
WARNING: This page is about a different car, the 1995 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
PCM continuously learns base idle position. This base idle position is the relationship of engine RPM to throttle position. PCM is limited to a fixed amount of learned throttle angle that it can apply. When this limit is reached, Code P085 will set. The cause of this increase in learned throttle angle is usually deposits in throttle body.