Throttle Body: Testing and Inspection

Minimum Air Flow Air Metering Fitting:

WARNING: Apply parking brake and/or block wheels before performing any engine running test with the vehicle on the ground.

PREPARATIONS

1. Remove air cleaner, and plug heated air door vacuum hose.
2. With vehicle in PARK (A/T) or NEUTRAL (M/T), START the engine, turn all accessories off, and allow engine to run until the cooling fan cycles at least once.
3. Shut OFF engine. Connect scan tool, timing light and tachometer.
4. Adjust basic timing. SEE IGNITION SYSTEM/ADJUSTMENTS

PROCEDURE

1. Disconnect PCV valve and attach metered orifice no. C-5004 (or equivalent 0.125 inch orifice) to intake manifold nipple.
2. START engine and allow to idle for at least one minute.
3. Using scan tool [1], access MINIMUM AIRFLOW IDLE SPEED TEST.

- The Idle Air Control (IAC) motor should close the bypass passage fully.
- Idle spark advance should become fixed.
- Idle fuel should become enriched.
- Engine rpm will be displayed on the scan tool.

4. Read idle rpm with tachometer, and compare to specifications below.

- If idle rpm is within range, Minimum Air Flow is set correctly.
- If idle rpm is not within specified range, replace the throttle body.

5. Shut engine OFF, remove metered orifice, timing light and tachometer. Install PCV valve hose, and air cleaner.

Remarks:

[1] Follow scan tool manufacturer's instructions for procedures.

ODOMETER READING IDLE SPEED

Less than 1000 miles 650-1,250 RPM
More than 1000 miles 1,050-1,250 RPM