GM Century/Lumina/Grand Prix/Intrigue 1997-2000

Throttle Body


The throttle body is part of the air intake system. It is basically a simple butterfly air valve (throttle plate) which controls the amount of air being delivered into the engine. The throttle body also mounts the Idle Air Control (IAC) valve, the Throttle Position (TP) sensor, Mass Air Flow (MAF) sensor on some engines, some vacuum line connections and water connections which heat the throttle body to prevent icing.


All of the engines covered by this guide use similar procedures for removing the throttle body. Some slight procedure variance (small clips or brackets, etc.) may exist. The following procedure should suffice for all vehicles.

  1. Disconnect the negative battery cable.
  3. Drain the cooling system into a suitable container.
  5. Remove the air intake tube (runs from the air cleaner to the throttle body).
  7. Detach the Idle Air Control (IAC) valve and Throttle Position (TP) sensor electrical connectors. Tag for identification and remove vacuum lines, as necessary.
  9. Remove the accelerator control and cruise control cables from the accelerator control cable bracket. Remove the bracket.
  11. Disconnect the throttle body coolant by-pass hoses.
  13. Remove the heater pipe nut at the throttle body.
  15. Remove the nuts and bolts holding the throttle body to the intake manifold and remove the throttle body from the vehicle. On some vehicles (3.8L engine in particular) a wrench should be used the manifold side of the threaded inserts to keep the inserts from rotating in the manifold casting.

Do not use solvent of any type when cleaning the gasket surfaces on the intake manifold and the throttle body assembly, as damage to the gasket surfaces and the throttle body assembly may result. Take great care not to damage the soft aluminum surfaces when cleaning the gasket surfaces. Sharp tools will damage the sealing surfaces.

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Fig. Typical throttle body arrangement-3.1L and 3.4L (VIN E) engines

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Fig. Exploded view of the throttle body mounting-3.4L (VIN X) engines

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Fig. Typical throttle body arrangement-3.5L (VIN H) and 3.8L engines

To install:

  1. Clean all parts well, especially the gasket sealing surfaces on the throttle body and the intake manifold. Inspect the retaining studs and the threaded inserts in the intake manifold, if used. Replace any damaged components as required.
  3. Using a new gasket, install the throttle body assembly and tighten the retaining bolts evenly to 19 ft. lbs. (25 Nm).
  5. Install all remaining components in the reverse order of removal. It is important that the throttle should operate freely without binding between full closed and wide open throttle. Inspect and check for complete throttle opening and closing positions by operating the accelerator pedal. Also check the carpet fit under the accelerator pedal.