Throttle Body: Testing and Inspection

Throttle Body Minimum Airflow Check:

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. 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.
2. Shut OFF engine. Connect scan tool, timing light and tachometer.
3. Adjust basic timing. SEE IGNITION SYSTEM/ADJUSTMENTS

PROCEDURE

1. With engine OFF, disconnect the 3/16" manifold vacuum purge hose from the top of throttle body and cap throttle body nipple.
2. START engine and allow it 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.

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 OFF the engine, disconnect tachometer, and timing light, and connect the vacuum hose to the throttle body.

Remarks:

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

ODOMETER READING IDLE SPEED

Less than 1000 miles 650-1,400 RPM
More than 1000 miles 700-1,400 RPM