Component Tests and General Diagnostics

Fig. 69 PCV Valve:

1. Warm engine in Park or Neutral until the cooling fan has cycled on and off at least once.
2. Ensure that all accessories are off.
3. Shut off engine.
4. Disconnect the PCV valve hose from the PCV valve (Fig. 69). Cap the PCV valve.

Fig. 70 Purge Hose:

5. Disconnect purge hose from the nipple on each throttle body (Fig. 70).

Fig. 71 Orifice 6457 Attached to Purge Nipples:

6. Use a piece of hose to attach an Air Metering Orifice 6457 (0.125 in. orifice) to the purge nipple on each throttle body (Fig. 71).
7. Connect the DRB scan tool to the data link connector inside the passenger compartment.
8. Restart the engine. Allow engine to idle for at least one minute.
9. Using the DRB, access Minimum Airflow Idle Speed.
10. The following will then occur:
- Idle air control motor will fully close
- Idle spark advance will become fixed
- DRB scan tool displays engine RPM
11. If idle RPM is within the range shown in the Idle Specification chart, throttle body minimum airflow is set correctly.
- If idle RPM is below specifications even though the idle air control motor operates normally and the throttle bodies were cleaned of coking and synchronized, replace the throttle bodies.
- If idle RPM is above specifications reset throttle body synchronization. Also, recheck idle air control motor operation using the DRB scan tool. If idle RPM is still above specifications after setting throttle body synchronization, check for leaking intake manifold plenum or gaskets.

IDLE SPECIFICATION CHART

Odometer Reading Idle Speed

Less than 1000 miles 700-1,000 RPM
More than 1000 miles 750-1,100 RPM

12. Shut off engine.
13. Remove orifice 6457 from each throttle body Install purge hoses.
14. Remove cap from PCV valve. Connect hose to PCV valve.
15. Remove DRB scan tool.