Throttle Body: Testing and Inspection

1. Remove the air cleaner assembly and plug the heated air door vacuum line. Connect a timing light and tachometer to the engine.
2. Connect the scan tool to the engine compartment diagnostic connector.
3. With vehicle on PARK (A/T) or NEUTRAL (M/T), START the engine and allow it to warm up until the cooling fan cycles at least once, then shut OFF the engine.
4. Disconnect the coolant temperature sensor and START the engine. Adjust basic timing to 12° BTDC ± 2°, then shut OFF the engine and reconnect the coolant temperature sensor.
5. Disconnect the PCV valve from the intake manifold nipple and install a 0.125" orifice (Miller Tool # 6457 or equivalent) to the intake manifold nipple.
6. START the engine and allow it to idle for at least one minute.
7. Using the scan tool, access the minimum idle air flow speed function. When this mode is entered, the following will occur:
a. Automatic Idle Air Speed (AIS) motor will fully close.
b. Idle spark advance will become fixed.
c. Idle fuel will be provided at a set value.
d. The engine rpm will be displayed on the scan tool.
8. Check the idle rpm with a tachometer. If the idle rpm is within the specifications listed below, the throttle body minimum air flow is correct. If it is not within the rpm range below, replace the throttle body.

ODOMETER READING IDLE SPEED

Less than 1000 miles 650-1250 RPM
More than 1000 miles 1050-1250 RPM

9. Shut OFF the engine and remove the scan tool, tachometer, and timing light from the engine.
10. Remove the orifice tool from the intake manifold and reinstall the PCV hose. Install the air cleaner and connect the heated air door vacuum hose.