Component Tests and General Diagnostics

Throttle Body Minimum Air Flow Check:

1. Start the engine and warm it up until the engine coolant is heated to 80°C (176°F) or higher and then stop the engine.
2. Disconnect the PCV valve hose from the intake manifold nipple.
3. Attach Air Metering Fitting 6457 (0.125 in. orifice) to the intake manifold nipple.
4. Disconnect the 3/16 inch idle purge line from the throttle body nipple.
- Cap the 3/16 inch nipple.
5. Connect the scan tool to the data link connector.
6. Restart the engine.
- Allow engine to idle for at least one minute.
- All accessories must be off.
7. Using the scan tool, access the ACTUATOR TEST "Minimum Airflow Idle Speed" screen.
8. The following will then occur:
- Idle air control motor will fully close.
- Idle spark advance will become fixed.
- Scan tool displays engine speed.
9. If idle speed is within the range shown, throttle body minimum airflow is set correctly.

Standard value:
- 450-1,100 r/min (Less than 1,000 Miles)
- 500-1,100 r/min (More than 1,000 Miles)

If idle speed is not within the standard value, use the scan tool to access the SPECIAL FUNCTION "Reset AC" screen and reset the IAC. Then carry out step 7 again.

10. If idle speed is above specifications, use the scan tool to check idle air control motor operation.
- If idle air control motor is OK, replace the throttle body.

NOTE: If the throttle body is replaced, reset the IAC.

If idle speed is below specifications, shut off the engine and clean the throttle body as follows:
a. Remove the throttle body from engine.

WARNING: Clean throttle body in a well-ventilated area. Wear rubber or butyl gloves. Do not let cleaner come in contact with eyes or skin. Avoid ingesting the cleaner. Wash thoroughly after using cleaner.

b. While holding the throttle open, spray the entire throttle body bore and the manifold side of the throttle plate with cleaner.

Fuel Pressure Test:

c. Using a soft scuff pad, clean the top and bottom of throttle body bore and the edges and manifold side of the throttle blade. The edges of the throttle blade and portions of the throttle bore that are closest to the throttle blade when closed, must be free of deposits.
d. Use compressed air to dry the throttle body.
e. Inspect throttle body for foreign material.
f. Install throttle body on manifold.
g. Repeat steps above. If the minimum air flow is still not within specifications, the problem is not caused by the throttle body.

11. Shut off engine.
12. Remove Air Metering Fitting 6457 from the intake manifold PCV nipple. Reinstall the PCV valve hose.
13. Uncap the throttle body idle purge nipple and connect the idle purge line.
14. Remove the scan tool.