Throttle Body: Testing and Inspection

Minimum Air Flow Air Metering Fitting:

Minimum Air Flow Connections:

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


Note: Before performing minimum air flow test, make sure all accessories are off.

1. With vehicle in PARK (A/T) or NEUTRAL (M/T), START the engine and allow it to warm up until the cooling fan cycles ON and OFF at least once, then shut OFF the engine.
2. Connect a timing light and tachometer to the engine.
3. Disconnect the coolant temperature sensor and START the engine. Adjust basic timing to 12° BTDC +/- 2°, then shut OFF the engine and connect the coolant temperature sensor.
4. Disconnect the PCV valve hose from the PCV valve and plug the PCV valve nipple.
5. Disconnect the idle purge hose from the engine vacuum harness tee and install a 0.125" orifice tube (Miller Tool# 6457 or equivalent) in the intake manifold mounted idle purge hose.
6. Connect the scan tool to the engine compartment diagnostic connector. START the engine and allow it to idle for at least one minute.
7. Using the scan tool, access the Minimum Airflow Idle Speed Test. When this mode is entered, the following will occur:
a. Idle Air Control (IAC) motor will fully close.
b. Idle spark advance will become fixed.
c. The engine rpm will be displayed on the scan tool.
8. Check the idle rpm with a tachometer. If the idle rpm is not within the range below. Clean throttle body and retest. SEE Fuel Delivery and Air Induction/ Component Service and Repair.
9. Shut OFF the engine; remove the scan tool, tachometer, timing light, and orifice tube; and connect the purge line and PCV valve to their respective ports.
10. Erase any fault codes that may have been set.

Note: If vehicle passes minimum airflow test, and still exhibits idle speed problems, perform Idle Air Control (IAC) motor actuation test using scan tool.


Odometer Reading Idle Speed

Less than 1000 miles 625-950 RPM
More than 1000 miles 750-950 RPM