Engine Controls - Remove/install/overhaul Audi 90 B4

INTRODUCTION

Removal, overhaul and installation procedures are covered in this article. If component removal and installation is primarily an unbolt and bolt-on procedure, only a torque specification may be furnished.

CRANKSHAFT POSITION SENSOR

The Crankshaft Position Sensor (CKP) is located on lower left rear side of cylinder block. Remove necessary components to access sensor. Remove sensor mounting bolt and sensor. To install, reverse removal procedure.

ENGINE SPEED SENSOR

Engine Speed Sensor is located on upper left rear side of cylinder block. (Scheme 1) Before removal, mark sensor mounting bracket for reassembly reference. Remove sensor mounting bolts and sensor. To install, reverse removal procedure.

Removal

Hall Sensor is located on rear of left cylinder head. (Scheme 1) Remove mounting bolts and sensor. To replace oil seal, remove hall sensor mounting plate. Install Seal Extractor Holder (2085/1) and Seal Extractor (3240). Remove seal.

Installation

Clean sealing surface. Install seal to the stop using Installer (3241). Install hall sensor mounting plate and Hall sensor.

KNOCK SENSOR

The knock sensors are located beneath intake manifold. The knock sensors can be removed without removing intake manifold. Using a long 8-mm Allen Wrench (3247), remove knock sensor mounting bolts and knock sensor. Reverse removal procedure to install. Tighten bolts to specification. See TORQUE SPECIFICATIONS at the end of this article.

Scheme 1

ELECTRONIC CONTROL UNIT (ECU)

The ECU is located in the passenger footwell on the back of the evaporator case. To remove, pull carpet back and remove cover of plastic housing containing ECU. Remove ECU from housing. To install, Reverse removal procedure.

FUEL SYSTEM

FUEL SYSTEM PRESSURE RELEASE

1. Remove fuel pump relay from fuse panel. Start engine. Let engine run until it stops. Turn ignition off. Disconnect negative battery terminal. Install fuel pump relay.
2. Use a rag to cover fuel system connection before disconnecting high pressure fuel system component for test or repair procedure. Some residual fuel pressure may still be in system.

FUEL INJECTORS

Disconnect negative battery cable. Disconnect fuel lines from fuel supply manifold. Remove manifold mounting bolts and lift fuel manifold with injectors. Remove injectors from fuel rail. (Scheme 2) To install, reverse removal procedure.

Scheme 2

FUEL PUMP

1. Fuel pump assembly is located inside fuel tank. Release fuel pressure from system. Remove luggage compartment access cover. Disconnect electrical connectors and fuel hoses at fuel tank.
2. Loosen retaining ring, and pull unit out of fuel tank. Remove fuel pump from sending unit assembly. To install, reverse removal procedure.

MASS AIRFLOW SENSOR

1. Remove air filter, and unscrew stop bracket. Using heat gun, heat locking compound on fastening bolt. Remove bolt slowly. DO NOT damage threads. Clean locking compound from bolt hole threads.
2. Install airflow sensor plate. Ensure 5 dimple marks are up. Lightly tighten self-locking screw. Ensure sensor plate is centered and rest position is correct. To complete installation, reverse removal procedure.

OXYGEN (O2) SENSOR

O2 sensors is mounted in the exhaust pipe in front of catalytic converters. Disconnect permanent pigtail from sensor. Ensure sensor is free of contaminants. Avoid using any cleaning solvents. Sensor may be difficult to remove when engine temperature is less than 118°F (48°C). Always use anti-seize compound on threads before installation. Tighten sensor to specification. See TORQUE SPECIFICATIONS table below.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS