1991 Audi 90 Service and Repair Manual

This manual is built specifically for the 1991 Audi 90, covering the 2.3L inline-five (engine code NG) and Base Sedan trim, so the specifications, wear limits, and repair sequences match what Audi actually published for this exact powertrain rather than a generic 90-series reference.

Engines covered

• 2.3L inline-five — SOHC, naturally aspirated, gasoline

Body styles covered

• 4-door sedan

Trims covered

• Base

Known issues on the 1991 Audi 90. Two recalls are on federal record for this model year. The first covers the transaxle: differential oil is lost over time to evaporation, and the resulting low fluid level causes premature bearing and gear wear, which can lead the drive wheels to lose power or, in extreme cases, the front wheels to lock and cause rapid deceleration and loss of vehicle control. The second covers the frontal airbag sensor and control module: some sensors do not meet Audi's durability standards over the vehicle's lifetime, and a malfunctioning sensor can cause the airbag to deploy without warning, risking loss of vehicle control. Owners have filed 3 complaints for the year. The factory diagnostic and repair procedures behind each of those systems are here.

From a slipping differential to an airbag sensor check, it keeps you on the OEM procedure and the correct specification for your specific 1991 Audi 90.