Diesel Data: Automotive Repair

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 at least once, then shut OFF the engine.
2. Connect a timing light and tachometer to the engine.
NOTE: When coolant temperature sensor is disconnected, the "Check Engine" light and cooling fan should come on and remain on throughout the procedure.
3. Disconnect the coolant temperature sensor and START engine. Adjust basic timing to 12° BTDC ± 2°, then shut OFF the engine and connect coolant temperature sensor.
4. Remove PCV valve and attach metered orifice no. 6457 (or equivalent) to intake manifold nipple.
5. 5. Connect the scan tool, START engine and allow to idle for at least one minute.
6. Using the scan tool, access MINIMUM AIRFLOW IDLE SPEED TEST. The following should occur:
a. Idle Air Control (IAC) motor will fully close.
b. Idle spark advance will become fixed.
c. Engine rpm will be displayed on the scan tool.
7. Confirm idle rpm with tachometer. If it is not within the range below, clean the throttle body and retest. SEE Powertrain Management/Fuel Delivery and Air Induction/Service and Repair
8. Shut OFF the engine; remove metered orifice, scan tool, and tachometer, and install PCV valve.
9. Erase any fault codes that may have been set.

ODOMETER READING IDLE SPEED

Less than 1000 miles 560-910 RPM
More than 1000 miles 610-910 RPM