NG 900/9-3 Throttle Body

Overview

The throttle body controls the flow of air into the intake. While driving, air flow is controlled by the throttle plate. At idle, through the electrically controlled IAC valve. The throttle body also has inlets for hoses from the evap. emission system purge valve, from the crankcase ventilation system (PCV), and vacuum lines leading the the manifold air pressure sensor (MAP), the fuel pressure regulator (FPR), and the turbo bypass valve (BPV). Note: hose connections for the non-turbo version of the engine, and later 9-3 models are different. Figs. 1 and 2

Fig. 1 - Throttle Body Overview

Fig. 2 - Throttle Body

Idle Air Control Valve

The IAC valve is a solenoid controlled valve which regulates the flow of air into the engine during idle. It may require cleaning every few years, and more often on engines where the crankcase ventilation system or the turbo leak an excessive amount of oil into the intake. For details see Michel Briand's Cleaning Directions. Fig. 3

Fig. 3 - Idle Air control Valve

Engine Coolant Connections

Engine coolant circulates through a section of the throttle body by way of two hoses connected to the engine, to help prevent freeze up during winter. Fig. 4

Fig. 4 - Coolant Connections

Throttle Position Sensor

The TPS is a rotary potentiometer which indicates the position of the throttle plate. With the connector unplugged, the resistance measured between pins 1 and 3 should change gradually between 2.5k Ohms with throttle plate closed, and 1.0k Ohms fully open. Fig. 6

Fig. 6 - Throttle Body

Throttle Body Connections

Numbers correspond with labels in Fig. 7 1 - Crankshaft ventilation hose (PCV) 2 - Air Pressure sensor (MAP) 3 - Fuel pressure regulator (FPR) 4 - Turbo bypass valve (BPV) 5 - Evap emission system purge valve 6 and 7 - IAC valve hoses 8 and 9 - Coolant hoses

Vacuum and PCV Lines

Fig. 7 - Throttle Body Connections

Bottom View

The vacuum lines are connected into two chambers at the bottom of the throttle body, which open into the intake manifold. Also note groove for the gasket between the throttle body and the manifold. Fig. 8

Fig. 8 - Throttle Body Bottom View

Cleaning and Lubrication

The inside of the throttle body may need cleaning every few years around the throttle plate. The throttle arm springs and bushing can stick and may require lubrication, and the throttle position sensor (TPS) can wear out. The tar around the circumference of the throttle plate is from the same source as the IAC valve contamination. Fig. 5

Fig. 5 - Throttle Body Cleaning

Part Numbers

• Idle Air Control Valve: 9127200 (SE Turbo, IAC valves on non-turbo, "S" models are different)
• Throttle Position Sensor:
  • 8857195 ('94-'95)
  • 4661062 ('96)
  • 9181538 ('97-'98)
• Intake Air Temp Sensor: 9174442
• Coolant Temp Snsr: 9182270, (side of the engine)
• Manifold Temp Snsr: 9177213, (under the fuel rail)